# Timing off. What gives?



## RMTZ67 (Mar 12, 2011)

So I was gonna check my initial timing since breaking in the engine. Started up on first hit on break in, The distributor is set where it runs its best by ear. I took the timing light to it and it was about 2" off the mark. I moved the dizzy and it don't get any closer . What gives? Is my dizzy one tooth off? I did install a new oem style damper from butler. Tried putting the timing light plug wire on the #2 and #8 wire just to see if it gets any closer to the mark, but it did not


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## GTO44 (Apr 11, 2016)

Very confusing to read... please restate your exact problem and members can be of better help


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## RMTZ67 (Mar 12, 2011)

GTO44 said:


> Very confusing to read... please restate your exact problem and members can be of better help


 After rebuilding the engine and attempting to set the timing with the vacuum hose removed and plugged. My damper mark is about 2" from TDC. Does not get closer but seems to idle decent. I installed a new balancer from butler during the rebuild.


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## GTO44 (Apr 11, 2016)

With any aftermarket balancer you should verify TDC and make sure the pointer and balancer match up. Put cylinder #1 at TDC. If the tdc mark on the balancer is not matching the pointer on your block then you need to get an adjustable timing pointer. Or use the factory pointer on the block side and add timing tape to your balancer. Here’s a link to some timing tape. This one has different strips for different size balancers and its only a few bucks 

https://www.summitracing.com/parts/...ezVWX-KjTENIZhwefllJ_zTqwnNyERSBoC9IUQAvD_BwE


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## RMTZ67 (Mar 12, 2011)

Both my timing chain gears were set at 12:00 position. New BP damper only goes on one way. Then set number one piston on compression stroke and TDC. then dropped the distributor facing close to the number 1 plug and started my firing order there going counter clockwise. Fired up on first hit on breakin. I removed vacuum from distributor and plugged it, Timing light wire on #1 plug. so anybody see any reason why my timing mark is so far from my marks on my timing cover?


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## Red Skeleton (Jul 2, 2019)

RMTZ67 said:


> After rebuilding the engine and attempting to set the timing with the vacuum hose removed and plugged. My damper mark is about 2" from TDC. Does not get closer but seems to idle decent. I installed a new balancer from butler during the rebuild.


So your saying that the mark does NOT move when you rotate the dizzy? Could it be a timing light issue? Could you be pushing the wrong button on the light?:surprise:


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## RMTZ67 (Mar 12, 2011)

Red Skeleton said:


> So your saying that the mark does NOT move when you rotate the dizzy? Could it be a timing light issue? Could you be pushing the wrong button on the light?:surprise:


It moves, but nowhere close. I tried two timing lights that I have and it is the same with both. I also tried connecting the timing light to the #8 and 2 wires just to see if it moved closer, but actually moved farther. I called butler and they are going to allow me to send the damper back and have it checked. Not sure what else it could be.


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## Red Skeleton (Jul 2, 2019)

So the light moves but no where close the the scale on the timing cover? FYI my 68 400 with a cam base timing is about 24 degrees BTDC at idle which is off the stock scale. Thant's where it runs best. So if you keep turning the dizzy it won't change at a certain point?


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## RMTZ67 (Mar 12, 2011)

Red Skeleton said:


> So the light moves but no where close the the scale on the timing cover? FYI my 68 400 with a cam base timing is about 24 degrees BTDC at idle which is off the stock scale. Thant's where it runs best. So if you keep turning the dizzy it won't change at a certain point?


 It moves, but like 6 degrees maybe


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## PontiacJim (Dec 29, 2012)

RMTZ67 said:


> It moves, but like 6 degrees maybe


Don't remember, so refresh my memory. Are you using the stock 9-bolt water pump or did you convert to the later 11-bolt?

Why I ask is that if you are using the factory style 2-piece '67 balancer and went with the updated 11-bolt water pump, the timing cover scales are different and would be off - '67 balancer with '68 and up timing cover would be a mismatch.


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## RMTZ67 (Mar 12, 2011)

PontiacJim said:


> Don't remember, so refresh my memory. Are you using the stock 8-bolt water pump or did you convert to the later 11-bolt?
> 
> Why I ask is that if you are using the factory style 2-piece '67 balancer and went with the updated 11-bolt water pump, the timing cover scales are different and would be off - '67 balancer with '68 and up timing cover would be a mismatch.


 It is still the stock 8 bolt.


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## Red Skeleton (Jul 2, 2019)

What I don't understand is why 6 degrees? You should be able to twist that distributor and make the timing mark move till the engine dies or it physically hits something.


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## RMTZ67 (Mar 12, 2011)

Red Skeleton said:


> What I don't understand is why 6 degrees? You should be able to twist that distributor and make the timing mark move till the engine dies or it physically hits something.


It will turn both ways till it dies but wont move the mark 2"


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## Red Skeleton (Jul 2, 2019)

To me it sounds light the timing light isn't getting the correct signal. Harmonic balancer has nothing to do with the strobe light moving, the distributor does. Unless the damper is loose or moving around? (not likely). 

Where are you grounding the light?


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## RMTZ67 (Mar 12, 2011)

Red Skeleton said:


> To me it sounds light the timing light isn't getting the correct signal. Harmonic balancer has nothing to do with the strobe light moving, the distributor does. Unless the damper is loose or moving around? (not likely).
> 
> Where are you grounding the light?


At the battery.Been forever since I used a timing light. not 100% sure there good. Should they both connect to the battery?


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## RMTZ67 (Mar 12, 2011)

New balancer from butler.


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## RMTZ67 (Mar 12, 2011)

I will try moving the number 3 wire away from the number 1 tomorrow, see if that changes anything. Thought the new damper could be off but when I set the distributor it fired right up the first time. I think I will rent another timing light from autozone tomorrow. Got to be something simple.its not rocket science lol.


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## Red Skeleton (Jul 2, 2019)

The battery. You could try grounding somewhere on the block, just for laughs. Jim knows about balancers and just about EVERYTHING else. He's the Obi one Kenobi of the forum 

You can temporarily time it by ear and advance it till the engine pings or the starter strains, then back off till they don't otherwise you'll damage the engine.


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## GTO44 (Apr 11, 2016)

Or..... you can find TDC on #1 and use timing tape on the balancer to calibrate it so you’re not timing in the dark...


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## cij911 (Oct 25, 2017)

You should be using cylinder 1 for your timing light. If you can move the distributor until the engine dies, then your timing is in fact changing and the issue is with your visual cues. You will need to follow GTO44's link and then use an adjustable timing light.


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## Paul Schiavon (Apr 22, 2014)

You installed the cam gear 180 degrees out of phase with the dot at the 12:00 o'clock position, it should have the dot at the 6:00 o'clock position and the crank gear's dot at the 12:00 o'clock position (dot to dot). When gears are dot to dot, the engine is actually at TDC of cylinder number 6 compression stroke and TDC of cylinder 1 exhaust stroke. Your timing marks are 180 out on the damper, that is why it is confusing you. To prove my point - put the timing light on cylinder number 6's spark plug wire to set your timing, it is incorrect but will work. To fix this error properly you need to remove the cam gear and reinstall it with the dot at the 6 0'clock position (dot to dot). Put cylinder 1's spark plug wire in the distributor cap location facing the driver's seat.


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## RMTZ67 (Mar 12, 2011)

Paul Schiavon said:


> You installed the cam gear 180 degrees out of phase with the dot at the 12:00 o'clock position, it should have the dot at the 6:00 o'clock position and the crank gear's dot at the 12:00 o'clock position (dot to dot). When gears are dot to dot, the engine is actually at TDC of cylinder number 6 compression stroke and TDC of cylinder 1 exhaust stroke. Your timing marks are 180 out on the damper, that is why it is confusing you. To prove my point - put the timing light on cylinder number 6's spark plug wire to set your timing, it is incorrect but will work. To fix this error properly you need to remove the cam gear and reinstall it with the dot at the 6 0'clock position (dot to dot). Put cylinder 1's spark plug wire in the distributor cap location facing the driver's seat.


 I set it per Rocky Rotella's book. But I tried it anyway and its actually in the same position as #1 . Tho I did try again to get it to tdc by turning the distributor and got it to tdc but was running pretty rough, but did not die. The carb has not been messed with since it was running last and used to run decent. So I am still at a loss.


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## PontiacJim (Dec 29, 2012)

First, let's clarify the timing "dots" on the cam/crank gear. Prior to 1967, the "dots" were shown to be positioned with the cam gear at 6 o'clock and the crank gear at 12 o'clock - or facing each other.

If I am correct, beginning in 1967 with the 400CI, the timing alignment went to 12 o'clock on the cam gear and 12 o'clock on the crank gear. 

Why? I don't know. I see in my '68 Service manual a photo of the rotor in the "No. 1 position" which is actually the No.6 position. HOWEVER, I can see some of the carb in the photo and it is a Rochester 4-Bbl which indicates an older engine, pre-1967. Manuals are sometimes not 100% accurate and do slip in some "older" photos. So the reason for th "dot" alignment change is most likely due to a re-design in the distributor - possibly the position of the vacuum advance and its relationship to the engine and its movement for adjustment?

However, either position will work, so no need to rip apart the timing cover and pull gears & chain. With the timing dots are aligned at 12 o'clock, the number 1 piston is put at the TDC firing position. When the dots are aligned with cam gear dot at 6 o'clock and crank gear at 12 o'clock, the number 6 piston is put at the TDC firing position - making the No. 6 the new No. 1 and then you follow your firing order from there (timing is 180 degrees off).

Of note, and mentioned this before, I used the dot-to-dot alignment on a '68 GTO gear/chain replacement thinking, and being told, that this was how you did it, right? Wrong. The engine would pop & sputter and sometimes almost run depending on where I moved the distributor. But, it would not start. So I parted out & junked a perfectly good running car (a $250 purchase back then) because I thought the engine bit the dust when the chain broke on me. If I had only known. :banghead: So that should clarify the timing gear "dot" alignment.

Seeing your engine is running, but timing off a bunch, my experience says it would not run at all, let alone pretty good, if the timing dots were 180 degrees off from the get go.

Make sure you are using the No.1 plug wire for timing and keep other wires away. I clamp my clamp down by the spark plug and away from other wires, not up top at the distributor cap.

To do the timing tape thing, I feel it wouldn't be as accurate as it could be with the best way to do this is right when you align your timing gears and use a timing wheel and piston stop with the heads off. This I would think to be the most accurate way to find TDC and then affix the timing tape as lined up with TDC on your timing cover indicator "0". Now i have never applied, nor used a timing tape, so my thinking on this may be wrong. I also have a timing wheel and piston stop and have never used them, but they look impressive in my Craftsmen tool box draw. LOL

You can certainly still get close using a piston stop that inserts into the spark plug hole and knowing both intake & exhaust valves are closed as the piston comes up on the compression stroke. This could be used to see if the timing gears were not aligned straight up as your timing mark on the balancer will be off. Here is one type of a piston stop: https://www.summitracing.com/parts/...MIypCv98SB5QIVjobACh1owgx7EAQYASABEgJusPD_BwE

There was a forum member (and I simply could not find the post as it may have been a spin-off of another post we had going) where his timing was also way off as yours. Turned out it was the crank gear. It had multiple keyway's so as to advance or retard the cam - many crank gears use this adjustability. He had misread the gear as it was poorly stamped and aligned a keyway marking when indeed the alignment dot was slightly to the left, and not having a keyway slot below it. He had even posted pictures and that was what I was looking for as you could see how lightly the correct alignment dot was stamped. Once he corrected that and put it all back together, the timing was perfect.

So this could be the issue if you used a crank gear having several keyway slots to advance or retard the timing of the cam through the crank gear. The piston stop as mentioned earlier might be an indicator of this before you go pulling things apart.

Found another "weird" fix on the H.A.M.B. website. A member was having the same experience. All kinds of suggestions, none of which worked. The fix? The distributor cap. It seems he installed an exact same second distributor to see if it was a defective distributor. Same results. Then for some reason he decided to try different parts on the distributor, part-by-part. First was the distributor cap swap with a different one he had. Bingo, timing went to where it should have been. So the cap (maybe made in China) was somehow causing an effect on the timing reading at the crank. I can't imagine how, but who knows. Very "weird" and I have never heard of such a thing, but......... So as simple as this sounds, maybe go to your favorite auto parts store and get another cap. If it works, great, if not, then you have a spare all ready to go when you change out the cap when it wears out. I like a distributor cap with the brass contacts over the aluminum. This is what I always try to get if available.

If me, I would not invest a lot of time in this as long as the engine ran good, no overheating/pinging, and you can time it by ear/feel. My last 400 build I could not get it to time using the timing mark on the balancer & timing cover no matter what I did. So I gave up and just timed by ear/seat of the pants. I am constantly learning things myself and when I tore the engine back down to inspect the damages (lost oil pressure), I learned at that time that I had a crank hub, not a harmonic balancer. The hub was used on later production 1970's low performance 400's. It was solid and very small in diameter, so it would not work on the 1972 timing gear cover's scale. It was a junkyard engine and bought that way be me and reassembled that way by me. Who knew? It ran fine, but always had a slight vibration, now I think I know why. :yesnod:

So it is up to you on how you want to proceed. You can continue checking your timing, timing advance - looking for worn/loose parts, stuck weights, weak/missing springs on the weights, new cap/rotor, or pull the timing cover and check the timing gears and dot alignment again. You could use a piston stop and see how close your timing marks actually are in alignment to verify the mark on the harmonic balancer is correct.

So whatever you try, keep us posted of the results and we should be able to narrow it down and get things right. :thumbsup:


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## RMTZ67 (Mar 12, 2011)

PontiacJim said:


> First, let's clarify the timing "dots" on the cam/crank gear. Prior to 1967, the "dots" were shown to be positioned with the cam gear at 6 o'clock and the crank gear at 12 o'clock - or facing each other.
> 
> If I am correct, beginning in 1967 with the 400CI, the timing alignment went to 12 o'clock on the cam gear and 12 o'clock on the crank gear.
> 
> ...


Glad I took pictures as I went through my build. Pretty much answers two questions anyway. I am gonna change out my distributor cap and rotor. Thats about the only thing I did not install new. I will see if napa has a piston stop also. Butler performance sent me a label and postage if I wanted to return the damper to get it checked. But I was thinking if I set it on tdc and dropped my distributor in and it fires up it must be good???? I tried a local auto parts store for a timing light rental (In case mine is off) but they don't have such a relic lol.


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## Lemans guy (Oct 14, 2014)

Just curved a distributor for a GTO and the dist cap felt tight but was not in the locks on the distributor,....I see this sometimes, I always check those locks on the cap with a mirror to make sure they are st correctly. A similar wrong set up could mess you up if cap spins independent of the distributor body.

Just a note the distributor gear has a dimple mark, it is there to index the distributor gear with the rotor tip. The rotor only goes on one way way with square and circle mating underneath, they can be forced wrong as well. Gear can be put on wrong and will cause dist vacumn can to hit intake.

Engine can be right and distributor can be put in 180 off as well. So make sure. Rotor and gear are on right, and rotor tip is not 180 off. It must be pointing at or just a few degrees before #1 spark plug, when #1 at TDC.

You can mistake tdc compression for tdc exhaust stroke, ...double check


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## Lemans guy (Oct 14, 2014)

Also make sure your distributor gear is on right and the roll pin has not fallen out, if so when you turn the dizzy nothing will happen...

Timing light inductive pickup is directional and must face spark plug....there is an arrow on it.


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## Red Skeleton (Jul 2, 2019)

Lemans guy said:


> Just curved a distributor for a GTO and the dist cap felt tight but was not in the locks on the distributor,....I see this sometimes, I always check those locks on the cap with a mirror to make sure they are st correctly. A similar wrong set up could mess you up if cap spins independent of the distributor body.
> 
> Just a note the distributor gear has a dimple mark, it is there to index the distributor gear with the rotor tip. The rotor only goes on one way way with square and circle mating underneath, they can be forced wrong as well. Gear can be put on wrong and will cause dist vacumn can to hit intake.
> 
> ...


"Just a note the distributor gear has a dimple mark, it is there to index the distributor gear with the rotor tip"

Can you clarify this as I'm rebuilding my distributor. The dimple and the rotor tip should point in the same direction?:surprise:


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## Lemans guy (Oct 14, 2014)

Red yes,...very simple put your rotor on first...make sure it is on correctly, square hole in square round in round!

They made it that way for guys like me! But they can be force fit and screwed on wrong,...so first verify it is on correctly.

Then lay your distributor on the bench, I use a rubber mat,...and point rotor tip straight up...

Now look down at the roto gear,..you should see a dimple on the gear also facing up., ...if so your gear is correctly indexed. 

If you don’t see it, lift it up, don’t bust the rotor tip and spin the gear 180,...is the dimple there? If so you need to reindex it.

Just face the rotor tip up agin and knock out the roll pin, spin the gear over so the dimple is up and insert the roll pin.

Don’t forget your shims.msince you are reworking it check the end play on the gear with a feeler gauge....GM spec is .15 thousandths on aluminum distributor and 10 thousands on cast iron. It is not engine work, does not have to be that exact.....when they start getting up in the 90 thousands gap they give timing problems, rebuilt ones usually come about 35 thousandths..

If you shim it use hardened dist shims, Moro’s sells packs of them for a few bucks.


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## Red Skeleton (Jul 2, 2019)

Lemans guy said:


> Red yes,...very simple put your rotor on first...make sure it is on correctly, square hole in square round in round!
> 
> They made it that way for guys like me! But they can be force fit and screwed on wrong,...so first verify it is on correctly.
> 
> ...


Great info! Mines 180 out. Also the end play is about a sixteenth of an inch! What I don't understand is that the thrust washer hardly looks worn at all:frown3:


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## RMTZ67 (Mar 12, 2011)

Lemans guy said:


> Just curved a distributor for a GTO and the dist cap felt tight but was not in the locks on the distributor,....I see this sometimes, I always check those locks on the cap with a mirror to make sure they are st correctly. A similar wrong set up could mess you up if cap spins independent of the distributor body.
> 
> Just a note the distributor gear has a dimple mark, it is there to index the distributor gear with the rotor tip. The rotor only goes on one way way with square and circle mating underneath, they can be forced wrong as well. Gear can be put on wrong and will cause dist vacumn can to hit intake.
> 
> ...


 I just installed a new cap and rotor since that was the only thing that was not replaced. Put it in correctly, Square to square. Set timing where it seems to (sound) the best, and the timing mark hits where the picture is of me using the timing light a few post back. Took it for a ride and seems to run well but temp is getting to the 210 mark after romping on it for a while. Temp seemed reasonable while crusin. Should I now advance it a bit at a time till it pings then back it off a touch. And will that cause it to get hotter ? Its got about 10 miles since break in. Also a little at the high end of 2nd at wot.


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## Lemans guy (Oct 14, 2014)

I think I would not be adding more timing until you can figure out your base timing. GTO44 and Red I think talked about using an adjustable timing mark and or timing tape. Timing tape is just a way to mark the balancer and read the timing off that. It is good because it goes out real far.

So if you set #1 at TDC Compression of course,...and if the balancer is not messed up,...then putting timing tape on would give you a way to measure where the timing currently is. Since the car starts after you put the tape on Fire it up, vac disconnected and plugged and at idle speed,..like 800 or so read where the strobe flashes on the tape. Say it is 12....well that is your base timing. 12 BTDC and where it is now.

Using GTO44 advice get an adjustable timing marker or improvise one with mechanics wire, or a coat hanger or a mark, and put it at the zero mark on the timing tape. 

That is zero because you already set the #1 at TDC and started the tape from there.......now use the new zero mark as TDC. It will then let you know how much you have advanced the base timing.

Once that is known, then you can use a prodcedure to rev it up to where it stops advancing and figure your total timing, centrifigal + base = total,...which you want at 36 and it can be fine tuned from there.

You strobe should fall somewhere on that timing tape, at least giving you a place to start. 

Now it the balancer is wrong this will. Be wrong so you already know you have to make sure that is right first.

You also could have a cracked or broken distributor, and it won’t rotate properly, so another r test is to just substitute a known good distributor and retry, maybe you already did that, but it will eliminate a lot of possibilities.

Your timing is changing when you turn it as the engine runs better or worse.

Keep at it you will get it!


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## Red Skeleton (Jul 2, 2019)

RMTZ67 said:


> I just installed a new cap and rotor since that was the only thing that was not replaced. Put it in correctly, Square to square. Set timing where it seems to (sound) the best, and the timing mark hits where the picture is of me using the timing light a few post back. Took it for a ride and seems to run well but temp is getting to the 210 mark after romping on it for a while. Temp seemed reasonable while crusin. Should I now advance it a bit at a time till it pings then back it off a touch. And will that cause it to get hotter ? Its got about 10 miles since break in. Also a little at the high end of 2nd at wot.


Yes, advanced timing will run cooler, retarded hotter.


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## RMTZ67 (Mar 12, 2011)

I will be getting a piston stop and a timing tape on monday. Speed shop just closed. So I would like to identify true tdc and and see where the mark on my new butler balancer lands. So I am just guessing now, my mark should land near tdc or close to it with a piston stop, not 2" away.After I get my timing squared away what should I tackle next? Distributor, carburetor? What order? Does anyone here rebuild distributors? Or is it prefered to have the car there? I was turning the advance on mine and it seemed like thos springs were a little tight. But what do I know. Been reading up on it tho.


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## PontiacJim (Dec 29, 2012)

RMTZ67 said:


> I will be getting a piston stop and a timing tape on monday. Speed shop just closed. So I would like to identify true tdc and and see where the mark on my new butler balancer lands. So I am just guessing now, my mark should land near tdc or close to it with a piston stop, not 2" away. After I get my timing squared away, what should I tackle next? Distributor, carburetor? What order? Does anyone here rebuild distributors or is it prefered to have the car there? I was turning the advance on mine and it seemed like those springs were a little strong. But what do I know . Been reading up some on it tho.


How about all of the above. 

The engine will probably run a little hot initially being new - things are tight and need to break/wear in.

You should be able to get pretty close to the TDC with the stop. Remove all the spark plugs so you have no compression fighting you. Then follow this YouTube video on how to mark the balancer, turning engine one way and then the other, and splitting the difference for TDC. https://www.google.com/search?clien...dead+center#kpvalbx=_xUSZXfOUHrKl_QbZ9bXYAQ31

Red Skeleton answered your question - advance timing can help to run the engine cooler, while retarding can cause the engine to run hotter. But don't use timing advance to cure another problem that may be causing the engine to run a little hot. 

Other factors can also cause the engine to run hotter - such as a lean condition.

Stomping on the car is going to make it run hotter as more air/fuel fills the cylinder and adds cylinder pressure, ie heat. So expect temps to rise and then cool after you are done hammering the engine. 

Never rebuilt a distributor, so can't help. Went new/aftermarket with my 455 build and have purchased rebuilt distributors from the auto parts store - then just run them as is, no fine tuning or tweaking. The only distributor I had set-up was the dual point on my 409 engine and it was set-up by the local machine shop using one of the Sun distributor machines, so I didn't have to do anything to it but run it.


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## RMTZ67 (Mar 12, 2011)

*Timing mark Dead nut! what gives?*



PontiacJim said:


> How about all of the above.
> 
> The engine will probably run a little hot initially being new - things are tight and need to break/wear in.
> 
> ...


 So I removed all my plugs, installed a piston stop aaaaaand. Its dead nut, if you split the difference on the two marks. But the timing light still shows it 2"' off when its running good. so its either a bad timing light or maybe a bad distributor.


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## RMTZ67 (Mar 12, 2011)

Here are the rest.


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## Red Skeleton (Jul 2, 2019)

Red Skeleton said:


> So the light moves but no where close the the scale on the timing cover? FYI my 68 400 with a cam base timing is about 24 degrees BTDC at idle which is off the stock scale. Thant's where it runs best. So if you keep turning the dizzy it won't change at a certain point?


Does your engine have a performance cam? If so see quote:wink3:


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## RMTZ67 (Mar 12, 2011)

Red Skeleton said:


> Does your engine have a performance cam? If so see quote:wink3:


I have a 068 cam. Would that cause it to read that way?


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## Red Skeleton (Jul 2, 2019)

RMTZ67 said:


> I have a 068 cam. Would that cause it to read that way?


I know nothing about hot cams. I do know mine has one and runs best at around 24 degrees at idle. I'd advance the timing to where it runs the best without pinging or hard starts, trial and error to get the most power. 

I'm still working on my timing because of low speed lurching but I'll get it one of these days!


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## Lemans guy (Oct 14, 2014)

Lurching or trailer hitching is often a symptom of too much advanced timing,... turning the timing up at idle just to get a smooth idle is a mistake ......without knowing the rest of the story.

These cars will run great at in a range of numbers including 24 degrees of timing at idle generally, but you must be grabbing at least 10 of that from vacumn timing.

If not and your base timing is 24, your centrifigal timing must be 12 or so. Most distributors are way over that, so make sure too much timing will cause detonation.

Don’t just turn up idle timing until it “Feels” good or “sounds” good,.....it should feel good and sound good and be correct throughout the power band.

You can make it feel and sound good at idle,...and it will lurch ping and detonate throughout the power band.

So make sure.


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## Red Skeleton (Jul 2, 2019)

Lemans guy said:


> Lurching or trailer hitching is often a symptom of too much advanced timing,... turning the timing up at idle just to get a smooth idle is a mistake ......without knowing the rest of the story.
> 
> These cars will run great at in a range of numbers including 24 degrees of timing at idle generally, but you must be grabbing at least 10 of that from vacumn timing.
> 
> ...


Thanks Lemans Guy. 
Logic would dictate that if I have some low speed lurching and no pinging and within 36 degrees total timing, that I should be able to pull the vacuum advance off to stop or minimize it-no go.
So I'm going to continue to retard the timing to see if I can time it out. My car is amazing in that I can't make it ping but can get to that other warning sign of a strained starter on startup but she still lurches:x.


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## Lemans guy (Oct 14, 2014)

Red do you have 24 degrees of base timing and 36 total? 

You can get too much timing too early and or to fast and you get the problems on acceleration as the springs may be so weak they pull centrifigal timing in on top of your base timing.

Or they just advance the weights so fast it lurches or pings etc.

I am sure you know your springs are on correctly. 

Just make sure you know when centrifigal starts and stops and how much,..lurching could be other things as well.


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## pcguy (Jul 7, 2014)

subscribed...


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## RMTZ67 (Mar 12, 2011)

So no one seems to be sure what causes the timing to be off two inches. So correct me if I am wrong. As long as I set it where it runs its best, I should set a timing tape on the balancer and get total timing from there? So all I would need to know is where is there? Hard to mark it while its turning lol.


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## Lemans guy (Oct 14, 2014)

So RM,...you have it mechanically at TDC, dead on......

So if you balancer is OK....Zero is at the Mark on the balancer

Put the timing tape starting there and make a corresponding mark on the engine.

So you have all three at zero.....The number one piston mechanically, ......

the balancer mark is now at zero with the piston..

Start the timing tape at balancer mark

And mark the engine next to to zero on tape and balancing mark....

Now try it and see where the timing light strobe falls........

You are setting the Advance timing light correct, right?.......

..if you set it for 10 degrees advance it will hit the strobe at zero on the balancer mark but read 10 degrees on the light......

Zero on the light should be zero on the balancer.


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## cij911 (Oct 25, 2017)

RMTZ67 said:


> So no one seems to be sure what causes the timing to be off two inches. So correct me if I am wrong. As long as I set it where it runs its best, I should set a timing tape on the balancer and get total timing from there? So all I would need to know is where is there? Hard to mark it while its turning lol.


If you have verified you are at TDC on #1 , then I would just mark the balancer with some white paint (paint pen works well) and then check what you are dealing with initial and total timing. That said, I suspect the dampener was installed incorrectly.


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## geeteeohguy (Feb 2, 2008)

Didn't read all the posts, but seemed to get the gist that with the piston at TDC Compression, the timing pointer on the cover is not aligned to the balancer mark. The mark is '2 inches' off from TDC. If this is the case, the only cause is the balancer itself: either the wrong one or the outer ring has slipped (common, especially on Chevies). The harmonic balancer hub is keyed into the crankshaft snout, and cannot be installed incorrectly. It WILL be in the right location on the crankshaft, and if not slipped or incorrect, it WILL have it's indicator meet TDC at the pointer if, indeed, the engine IS at TDC COMPRESSION. (not exhaust). 
My bet: wrong or slipped balancer.


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## RMTZ67 (Mar 12, 2011)

geeteeohguy said:


> Didn't read all the posts, but seemed to get the gist that with the piston at TDC Compression, the timing pointer on the cover is not aligned to the balancer mark. The mark is '2 inches' off from TDC. If this is the case, the only cause is the balancer itself: either the wrong one or the outer ring has slipped (common, especially on Chevies). The harmonic balancer hub is keyed into the crankshaft snout, and cannot be installed incorrectly. It WILL be in the right location on the crankshaft, and if not slipped or incorrect, it WILL have it's indicator meet TDC at the pointer if, indeed, the engine IS at TDC COMPRESSION. (not exhaust).
> My bet: wrong or slipped balancer.


The balancer is a new one from butler, and only installs one way on the crank. When I used a piston stop and I mark it on the balancer at stop both ways, and split the difference the mark on the balancer is dead on with the tdc mark on the timing cover. The issue is, when set the distributor to run well or use a vacuum gauge it is about 2" from tdc. If I try to move it near tdc it wants to die.I only have a 068 cam, nothing crazy. So why would it read that way? I have two timing lights and both read it in the same place. It runs well which is not the issue. I would just like to be able to read it on the #s or at least find out what causes this. So far searches only tell me if it runs well yada yada yada... no real answer.


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## cij911 (Oct 25, 2017)

RMTZ67 said:


> The balancer is a new one from butler, and only installs one way on the crank. When I used a piston stop and I mark it on the balancer at stop both ways, and split the difference the mark on the balancer is dead on with the tdc mark on the timing cover. The issue is, when set the distributor to run well or use a vacuum gauge it is about 2" from tdc. If I try to move it near tdc it wants to die.I only have a 068 cam, nothing crazy. So why would it read that way? I have two timing lights and both read it in the same place. It runs well which is not the issue. I would just like to be able to read it on the #s or at least find out what causes this. So far searches only tell me if it runs well yada yada yada... no real answer.


Who installed your cam? And have you verified it was properly degreed? Since you know the balancer is correct, that tells me your cam timing is off....

Here is a good video :


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## Lemans guy (Oct 14, 2014)

If the balancer is at the zero mark on the timing cover when the piston is at TDC....it is correct

When it runs correctly the timing advances to 10, 15, 20, degrees before TDC that moves the mark away from zero...

The correctly running timing is not zero, but a significant number of degrees before zero.

Put timing tape on balancer starting at zero....

Then shoot it with the strobe and read the number on the tape that is your timing advance.....should be a number of degrees before TDC or 2” as you describe...leave the timing light at 0 no advance.....

Then try.


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## pcguy (Jul 7, 2014)

One other test (didn't read where it was performed). I always get to TDC by putting my finger (or a compressor gauge) in the spark plug hole. That way you can tell where the valves are when the piston is coming up. Using your finger will cause it to be blown out just b4 TDC. Just a thought.

Agree with the previous post; can you tell us what the advance in degrees is re the 2" gap?

Nick


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## RMTZ67 (Mar 12, 2011)

pcguy said:


> One other test (didn't read where it was performed). I always get to TDC by putting my finger (or a compressor gauge) in the spark plug hole. That way you can tell where the valves are when the piston is coming up. Using your finger will cause it to be blown out just b4 TDC. Just a thought.
> 
> Agree with the previous post; can you tell us what the advance in degrees is re the 2" gap?
> 
> Nick


 I installed the cam. Did not degree the cam. So if this swap meet find timing light is proper for a 8cyl application. Because it has 2/4 stroke on it. I advance to 31 for the timing mark to be on tdc. Is this a correct timing advance light? When it's on 0 it reads the same as my base timing light. 2" off.


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## geeteeohguy (Feb 2, 2008)

What cij911 said. If you're bothered by it, time to check the cam timing...could be retarded 4 degrees. If it otherwise runs fine, I would be inclined to time it by ear/vacuum and drive it. Normally a retarded cam will run soft on the bottom end and strong on the top end. How does your engine RUN?


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## geeteeohguy (Feb 2, 2008)

I'll also add this: I wonder where the mark would be if you installed a factory original balancer assembly? Aftermarket parts, no matter who makes them, tend to have 'issues' that original parts in good condition do not. Cranks, balancers, head bolts, ignition systems, and on and on.


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## pcguy (Jul 7, 2014)

geeteeohguy said:


> I'll also add this: I wonder where the mark would be if you installed a factory original balancer assembly? Aftermarket parts, no matter who makes them, tend to have 'issues' that original parts in good condition do not. Cranks, balancers, head bolts, ignition systems, and on and on.


Totally agree with the above; the part could also be for another engine???


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## Lemans guy (Oct 14, 2014)

When you have the timing light on 31 and the strobe hits zero....That is 31 degrees of timing advance....

That would be very possible with a hot cam

Can you turn it to 20 and still run?


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## Lemans guy (Oct 14, 2014)

You are just reading the advance....

At 31 it would be about 2” off zero...

Nobody reads timing by inches....so it is confusing....use the timing tape you already have and verify your light with the tape...

Then you will know that your timing light is right

Sounds like it is all ok, but don’t drive it with 31 degrees base if you don’t know what your Centrifigal timing is...


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## cij911 (Oct 25, 2017)

RMTZ67 said:


> I installed the cam. Did not degree the cam. So if this swap meet find timing light is proper for a 8cyl application. Because it has 2/4 stroke on it. I advance to 31 for the timing mark to be on tdc. Is this a correct timing advance light? When it's on 0 it reads the same as my base timing light. 2" off.


Well if you did not degree your cam, there lies your problem....Sorry but you cannot just drop the cam in.


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## RMTZ67 (Mar 12, 2011)

Readjusted my valve lash this weekend and took it for a spin. seems to run run really well, both top and bottom end. Tho it seems to hold back some at wot before shifting gears. I guess I should of seen at what rpms. But the question I had is, after using a piston stop turned both ways to stop. The lower of the two factory type marks is my tdc. So is that where I should put my 0 on the timing tape then while doing the initial timing as in the pic should I fab a pointer to hit at the zero. Hope I am making sense.


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## Lemans guy (Oct 14, 2014)

Right put your timing tape at the lower mark which you know is TDC #1 Compression......that is zero, no need right now for a mark....

Disconnect and plug vac advance...

Now don’t move the dist start it up and with timing light with no advance, at zero, read your timing advance at the tape. If it is 30’ see if you can get 20 then 10....that is your base timing.

As you increase say to 30 you also increase RPM and may be adding centrifigal timing, so at 30 what is rpm? At 20. At 10....

You also then use the advance on the timing light to check it, set the light to 10......it should hit the mark at zero with 10 showing on the light,

Same with 20 or any number, the light will strobe the zero mark and show the advance on back of the light

Your timing tape and light should be the same or very close.


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## Lemans guy (Oct 14, 2014)

And when I say at first read the tape at 30 and now see if you can get 20 then 10 that is by turning the distributor,


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## PontiacJim (Dec 29, 2012)

Lemans guy said:


> Right put your timing tape at the lower mark which you know is TDC #1 Compression......that is zero, no need right now for a mark....
> 
> Disconnect and plug vac advance...
> 
> ...


Everything is correct, but might need some clarification - no offense *Lemans guy*. :grouphug:

Put the "0" degree of your timing tape where the lower line/mark is on your balancer - which is your TDC/0 degree position of the piston.

With the vacuum line disconnected to the distributor and the line plugged at the source of the vacuum so it cannot suck in any air, start the engine. Then with your adjustable timing light, make sure it is set at "0" degrees. You are going to see exactly what your engine timing is with the distributor as it is now installed - seeing you said it runs well. Your engine should also be adjusted for about 750 RPM's at idle. As idle increases, mechanical advance will begin to kick in and will have an effect on the initial reading, so you want about 750 RPM's at idle for this procedure/test.

If for example the timing tape reads 30 degrees BTDC at the "0" mark on the timing cover scale, then your engine is indeed running at 30 degrees BTDC. It may not be 30 because you will not know until you check it. It could be 23, or 32, or 17, or..... etc.. You are wanting to know what it is as it runs now. Write that number down should you need to go back to that setting.

Once you have that number, see if you can drop it down to a lesser advance by manually turning the distributor clockwise (left). Clockwise will retard the timing and drop the advance number reading at the timing cover scale mark/timing tape. Turning counter clockwise (right) will advance timing and the scale number will increase.

Manually turn the distributor with the engine running and the timing light (still set on "0") shooting at the timing tape/0 mark on the timing cover. As you slowly rotate the distributor left, you will see the timing tape degree numbers drop down heading towards the "0" mark on the timing cover scale. What *Lemans guy* was saying is as an example, IF your timing was at 30 degrees when you first fired up the engine, rotate the distributor left and see if you can drop the timing tape down to show 20 degrees as lined up on the timing cover scale "0". If it still sounds good and smooth, you are heading in the right direction.

If you can drop it to 20 degrees, see if you can continue and drop the timing down to around 10 degrees and see how it runs. Now as you drop the timing down, your engine's idle RPM's will most likely drop down as well. So you may want to increase your idle up to get you around 750 RPM's at idle at 10 degrees.

Why 10 degrees? Once you reconnect your distributor vacuum advance, and assuming it is hooked up to a direct port (constant engine vacuum), your idle timing will increase - generally about 10-12 degrees additional. So if you have dropped your initial at the balancer down to 10 degrees without vacuum advance and then connect the vacuum to the distributor, your timing on the balancer should jump right up to around 20-22 degrees which is right were you should want it to be. You can check this with the timing light once you reconnect the distributor vacuum line.

If you can get 20-22 degrees at the balancer with the vacuum hooked up, your idle may have now sped up on you as idle will increase as timing increases. So if needed, reset your idle speed again to about 750 RPM's. This is a general number as some cams may need more and the engine may run better at 800-950 RPM's, but you don't want it that high at this time. 

You can adjust the idle mixture screws later once you get the timing set and operating correctly - this will be another area to dial in.

IF you can get the initial timing set to 20-22 degrees BTDC and the engine seems to run smooth and sounds good, tighten the distributor down so it doesn't move from that setting.

The next step would be to work on the advance curve. This is where the dial-back feature of the timing light will come in.

Disconnect the vacuum advance again for this test. Disregard that the engine's initial will drop back down to 10 degrees. Don't adjust the idle unless you need to raise it to keep the engine running. The idle RPM won't matter for this test because you will be running the engine above idle speeds.

Set the timing light to an initial 34 degrees on the scale. How this works is whatever you set the timing light scale to, ie 34 degrees, when you shoot the balancer at RPM's you want max total timing in at, the timing tape should show "0" lined up with the "0" mark on the timing cover scale. You are essentially using the timing gun to be what the timing mark would show at the balancer. So whatever you set the timing gun scale to, you should see "0" lined up on the balancer at the RPM you want your Initial timing at the balancer (20 degrees) plus the distributor's mechanical weight advance (12-14 degrees there about) to give you a total advance of 34 degrees at a maximum of "X" RPM's.

Ok, so you want 34 degrees of total advance to be all in by about 3,000 - 3,200 RPM's (you could go more to about 3,500 RPM's, but I don't think any less than 3,000 RPM's).

With the timing light dial showing 34 degrees, shoot the timing mark at the balancer and bring your engine RPM's up to 3,000 RPM's. The timing mark on the balancer should be close to "0". If not quite there, slowly increase engine RPM's until you see "0" on the balancer and note your engine's RPM. If it happens to be less than 3,000 RPM's or more than 3,000 RPM's, this is where the adjustments are made either using assorted springs on the mechanical weights or a stop/bushing to limit total advance. This has been covered before.

If you can get to this point and write down all the info, ie "X" degrees of Initial advance _without_ vacuum, "X" degrees of Initial advance _with vacuum_, & total advance - 34 degrees at "X" RPM's, post your numbers here so we can look at them and then advise from there.

You can also reconnect your vacuum advance and readjust the idle if needed.

If you cannot get these numbers, it could mean a problem within the distributor such as bad/wrong vacuum canister or mechanical advance weights in the distributor not working or stuck, or they may need a stop to limit the total advance.

Now this is a general/basic set-up which may need more fine tune adjusting, such as retarding the initial timing and/or vacuum advance back to 16-20 degrees to prevent any detonation (pinging) under load out on the road, or adjusting the advance curve of the distributor to work with the adjusted initial timing. So don't assume this is gospel to your engine requirements. This is a general set-up to help you and us here in getting your engine timing to where it works best once all things are sorted out.

Hopefully *Lemans guy* will proof read this and add any needed comments, suggestions, or corrections if I got something wrong. :thumbsup:


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## Lemans guy (Oct 14, 2014)

No proof reading needed! This is how you find out what your timing is now. I would just build on what PJ said by saying the same thing a different way......

There are three timing areas and at the moment for you all three of them are unknowns,.....

1) So to find base timing just follow PJ instructions using the timing tape and then the timing light.....Base set with your hand will now be known.

2) once that is done hook up your vacumn can to full manifold vacumn and read the timing on the tape or light or both......now that will be known,.....again PJ lays out the procedure.

3) is Centrifigal timing,...it is fixed, it is mechanical, it is now some unknown number.......to find it easily (Engine Off) remove one spring on the weights under the distributor cap, leave both weights on, reattach the distributor cap. Now start the car and rev it up a helper is good here, and with the timing light or tape what you are looking for is when the timing STOPS advancing.

It will reach it’s centrifigal limit early because you removed one of the weights, you will not have to rev it too high.

Now you have this number where it STOPPED advancing....subtract your base timing from that number and that is your centrifigal #3 
REPLACE THE SPRING NOW, engine off.

Once all of these are known you can do more things as PJ allowed, see when the springs bring in the timing how fast how slow etc and you can work on the curve.

But if don’t have these 3 numbers you cannot deal with a curve, or anything else.

So retackle it go slow & work to discover all three of your key timing numbers, once you know them you can deal with them to keep or improve them.:nerd:


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## Lemans guy (Oct 14, 2014)

Correction...because you removed one of the “springs” not weights sorry


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## Lemans guy (Oct 14, 2014)

Oh and turn against rotation to advance timing.......

Don’t worry watch the strobe, if is not going the way you want turn the distributor the other way....


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## RMTZ67 (Mar 12, 2011)

Very clearly put guys. I set aside saturday just for this. If I can jump on this in bits at a time during the week it will help lighten the load on sat. I'll report back once I have those numbers. Thanks Lemans guy, PJ.


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## RMTZ67 (Mar 12, 2011)

so this is what I know now. And if I should go ahead and follow thru with what PJ mentioned (Try to get down to 20 then 10 ) let me know. just didn't have as much time as I was planning on sat. My base timing is 33 with full manifold vacuum. When I remove the vacuum and plug it drops to 24. Then with the vacuum still plugged and one advance spring removed I am all in @ 41. My timing tape is on tdc @ 0. Identified by going both ways using a piston stop and finding center of both marks.


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## cij911 (Oct 25, 2017)

RMTZ67 said:


> so this is what I know now. And if I should go ahead and follow thru with what PJ mentioned (Try to get down to 20 then 10 ) let me know. just didn't have as much time as I was planning on sat. My base timing is 33 with full manifold vacuum. When I remove the vacuum and plug it drops to 24. Then with the vacuum still plugged and one advance spring removed I am all in @ 41. My timing tape is on tdc @ 0. Identified by going both ways using a piston stop and finding center of both marks.


That sounds great. You may want to play with it on the dyno and see if running that much timing (41*) is acceptable, but if you're not pinging and the car feels great, them you are probably perfect (especially since you did not degree the cam when you installed it).


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## RMTZ67 (Mar 12, 2011)

Well it seems to be running good. But unsure if it can run better. Also wondering about purchasing a new distributor or maybe someone here rebuilds them.


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## Lemans guy (Oct 14, 2014)

RM ok you have your numbers....

Centrifugal is 17 degrees

Base should be correctly set at 19 ( Vac disconnected and plugged) to give you 36 Total

Then add vac advance yours is 9 degrees......(33 - 24 as you described)

Your idle timing will now be 19 base + 9 vac for 28 degrees......your car will idle properly here set Rpm with that timing correctly.

Now get a curve kit about $15 Bucks from Summit or JEGS and use one light and one medium spring,....usually a silver spring and a bronze spring.

This should get you real nice, you can check with your timing light exactly where that all falls and there will be slight variations, but in general
It will be starting at 1000 Rpm and all in by 3000 to 3500

Now drive it, and listen for pinging if none drive it awhile before making changes, a light pedal should give you nice acceleration and good all around performance.

Don’t make the mistake that more advance is better, more advance can cause poor running misfiring at the wrong time, or inefficient because it is too early or too late....

Start here and you can build on that.....


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## bigD (Jul 21, 2016)

cij911 said:


> Well if you did not degree your cam, there lies your problem....Sorry but you cannot just drop the cam in.


Yes, you CAN just drop it in. It has been done many millions of times, over the last 50+ years.

Obviously, it's better to degree it, IF you have all the tools & knowledge to do it. 

But, unless the cam maker ground the cam wrong, it will be close enuff, without precise degreeing.

I've never degreed a cam, & don't have the tools or know-how. And at my age, never plan to learn. 

I've also rebuilt engines by using a ridge reamer & flex hone. Have also built several 455 bracket engines, using boxed crank/bearing kits, TRW forged pistons, stock cast rods, & never balanced any of 'em. Ran 12's & high 11's & won lots of races.

There are lots of things that many today assume are absolutely necessary, which are not. Low buck, shade tree mechanics & drag racers have been doing it the "wrong" way for a long time. 

I'm not recommending the old way to everybody. Just saying that some things that are done today may not be absolutely necessary, in all cases. Have it done correctly, if you can afford it. 

Just out of curiosity, for those of you who have been degreeing all your cams , for a long time, how many name brand shelf cams have you found to be ground wrong ? By how much ? To degree a cam precisely, do you need one of the timings sets with 9 keyways. Or, can you usually do it with offset keys ?


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## cij911 (Oct 25, 2017)

bigD said:


> Just out of curiosity, for those of you who have been degreeing all your cams , for a long time, how many name brand shelf cams have you found to be ground wrong ? By how much ? To degree a cam precisely, do you need one of the timings sets with 9 keyways. Or, can you usually do it with offset keys ?


BigD - Watch the video that I posted, the cam was off and needed to be degreed ....IIRC it was off more than 6* and I have been told by friends that install and degree a lot, repeatedly say that other manufacturers are very inconsistent - one batch good and another way off. So while one technically can just install the cam, without it degreed properly, one is gambling.


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## RMTZ67 (Mar 12, 2011)

cij911 said:


> BigD - Watch the video that I posted, the cam was off and needed to be degreed ....IIRC it was off more than 6* and I have been told by friends that install and degree a lot, repeatedly say that other manufacturers are very inconsistent - one batch good and another way off. So while one technically can just install the cam, without it degreed properly, one is gambling.


 Well I had the same thoughts as BigD when you first wrote the quote, just did not put it to words. In the good ol days being the seventies for me, I never degreed a cam and never remember breaking in my cam @ 2800 rpms. But then again I don't remember a lot of things from those days lol. But I believe you are correct in "taking a chance" on installing the cam without degreeing it. And probably the difference from those days to now is most everything was made in the good ol USA. You could count on quality. Now you don't even know what your getting and from where. Like you said "it's a gamble". I also took a hell of a gamble to decide to put my engine together myself, not having rebuilt an engine in the last 40 yrs. But I figured I could do it three times myself, at the cost of someone else doing it. And it still be a gamble. So I decided I would give it a go. So far so good,THANKS to all of you that took the time to help me along. I still have a ways to go to get it fine tuned. Looking forward to learning more about timing advance and recurving distributors. Thanks again guys. RM


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## geeteeohguy (Feb 2, 2008)

Excellent point, RM. I'm pretty much in the same camp as Bigd.....Just built them and ran them. The 389 in my '65 I built in 1981 is still running strong, as is the 400 in my '67 I built in 1988. Neither one has a degree'd cam. Hell, I haven't even pulled the valve covers on the '65 since I installed it! ( I resealed the '67 8 years ago because it was all leaky). You are correct in that 20-30-40 years ago, you could simply buy new parts and KNOW that they would fit right and work as well as factory parts. Without a thought. Today, you have to do hours of research just to find a cam and lifters that won't fail in the first 1000 miles. Terrible.


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## PontiacJim (Dec 29, 2012)

Just a simple question to cover all reasons for the strange timing mark numbers. Did you use a timing tape specific to your balancer diameter? They have different calibrations depending on the balancer diameter. Yours should be the smaller 5.25" diameter balancer for '67 while the '68 and up are 6.75" diameter. https://butlerperformance.com/i-307...o-8-in-dia-msd-8985.html?ref=category:1234723

MY opinion on this, but 41 degrees total is probably too much, but you did not say what RPM your total is all in once you hooked your advance weight springs back up?

I have read that the closed chamber heads (Pontiac, Mopar, Chevy, etc.) can tolerate higher advance numbers versus an open chamber head, but I think I would drop the initial on the balancer down to about 22 which will drop your total a like amount, to 39, or possibly try 21/38 which is what I would shoot for.

Bottom line is that if it works for you and you don't have any detonation, hard start issues, or running hot, then you are probably good to go. You can give it a road test just to make sure. Do a quick run with no vacuum - distributor line unhooked and carb plugged so you are running on just the mechanical advance, then at a low RPM for 2nd gear, do a WOT run listening for any detonation. Try the same thing in 3rd. You want to lug the engine and make it work, so you want your RPM's a little on the low side for each gear (but still comfortable for that gear) and pull the car hard through that gear.

If all is well, hook up your vacuum advance and leave it at that and enjoy! :thumbsup:


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## geeteeohguy (Feb 2, 2008)

Jim, the closed chambered heads like and need more advance to be their most efficient....but that doesn't mean they can tolerate higher advance numbers on today's fuels. I made more power with my '67 when I ran the original 670 heads in the '80's....but it was ping city, even back then. A change to #12 's didn't help, either. Finally had to go with an open chamber 87cc head #15 off a '70 455....to be able to run a normal advance curve on 91 octane. I can't imagine trying to run 670 heads in arid central CA where I am on 91 gasohol.....the timing would need to be set at 10 degrees ATDC!!!


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## RMTZ67 (Mar 12, 2011)

PontiacJim said:


> Just a simple question to cover all reasons for the strange timing mark numbers. Did you use a timing tape specific to your balancer diameter? They have different calibrations depending on the balancer diameter. Yours should be the smaller 5.25" diameter balancer for '67 while the '68 and up are 6.75" diameter. https://butlerperformance.com/i-307...o-8-in-dia-msd-8985.html?ref=category:1234723
> 
> MY opinion on this, but 41 degrees total is probably too much, but you did not say what RPM your total is all in once you hooked your advance weight springs back up?
> 
> ...


Seems to run decent, but I am going to purchase a remanufactured points distributor, a a cap and rotor with brass terminals, a new coil and 8mm spark plug wires. I also ordered the dizzy spring set just in case. I will get that all installed and go from there. I got my timing advance #'s with one spring. When I get those new parts installed, should I just leave the springs on and get my full advance #'s and rpms? Could it be that maybe my 41 advance has to do with my compression being lowered to 9.6:1 and altitude being 5000? 
Stock 400
9.6:1 compression
670 heads
068 cam
ram air manifolds
2.5" exhaust
And yes,used 5.25 tape.


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## Lemans guy (Oct 14, 2014)

New rebuilt distributor will require you to find out what the centrifugal advance is on that one.

Since you are buying the curve kit, take off the two stiff springs that come with it and put on ONE medium silver spring from the kit.

Recheck your total advance, same way. My guess, it will be 32 or so centrifigal, where you have 17 now.

If so you will need to use the brass bushing in the curve kit and put it on the post, usually will take 2 to 8 degrees timing out of centrifigal.

Say it takes out 6, then you will have 26 inside, the only way to know is with a test. Taking off a spring just saves you from having to rev the engine up so high.....

You do lean the mixture at higher altitude to keep the gas in the correct AFR ratio”, if you adjust the carb or the fuel injection to keep the mixture correct, say 13.5 at cruise,...timing just interacts with the correct mixture, just like it would at sea level

But if your mixture is too lean advanced timing is better for firing a leaner mixture, but a too lean mixture is very bad for your engine, creates heat and can cause detonation, and the detonation will cause heat and you get in a circle.

Are you in Colorado? Take your distributor over to Lars he will set it up for you, he is the best there is. Email him @ [email protected]

You are very close to having a real good runner there and good luck!


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## PontiacJim (Dec 29, 2012)

* RMTZ67*: "and altitude being 5000?"

*PJ*: You just solved a lot of head scratching. At an altitude of 5,000 feet, the air is not as dense - the denser the incoming air, the more pressure that will be developed when it is compressed. This excerpt may help:

"Altitude has an effect on cylinder pressure and is not often considered when building an engine. As altitude gets higher, the cylinder pressure drops. Cylinder pressure starts to really become affected when the altitude begins to get around 1200’ – 1500’. Higher altitudes may need 12:1 or 13:1 compression in order to use 92 octane with their combination. This may soud contradictory to what most of us know or are familiar with and that is why it is important to understand cylinder pressure. It is not unheard of for a street engine to run over 14:1 on 91 octane because they are at a 6,000’ altitude, have aluminum heads and a BIG cam. At this high of an altitude, cylinder pressures need to be increased by using higher compression pistons which would be too high and a real problem on 91 octane if the altitude were 1,000'."

So everything changes at 5,000 feet and this is probably why you can run on pump gas without detonation and use the advance numbers you are seeing. Drop down to sea level, and you are going to have a big problem.

:thumbsup:


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## gmjunkie (Jan 1, 2019)

bigD said:


> Yes, you CAN just drop it in. It has been done many millions of times, over the last 50+ years.
> 
> Obviously, it's better to degree it, IF you have all the tools & knowledge to do it.
> 
> ...




Take a look at this link 



This is my buick 350 when I couldnt figure out why it was running so rough. After talking to the cam manufacturer he recommended I double check to make sure the cam was degreed properly. Easy to do, even with the heads on. Only need a dial indicator and I made a degree wheel out of cardboard and a printed degree wheel I glued to the cardboard. It was 100% good enough to give me consistent numbers. 

Turns out the cam was ground 4 degrees retarted and installed straight up ( dot to dot) and that was my issue. Especially since the manufacturer says this cam is recommended to be installed 4 degrees advanced... i was 8 degrees away from where I should have been. In my case I did buy a 9 keyway sprocket, however, Ive been told that's not necessary. If you know what you're doing, you can simply advance the teeth on the chains, just have to double check your work when you're done to confirm you are where you need to be with your adjustment. 

After this adjustment the idle smoothed right out. Still have some carb tuning to do, but boy did this make a night and day difference. 

POI the cam was manufactured by TA performance


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## RMTZ67 (Mar 12, 2011)

gmjunkie said:


> Take a look at this link https://www.youtube.com/watch?v=SWC-sl0id30
> This is my buick 350 when I couldnt figure out why it was running so rough. After talking to the cam manufacturer he recommended I double check to make sure the cam was degreed properly. Easy to do, even with the heads on. Only need a dial indicator and I made a degree wheel out of cardboard and a printed degree wheel I glued to the cardboard. It was 100% good enough to give me consistent numbers.
> 
> Turns out the cam was ground 4 degrees retarted and installed straight up ( dot to dot) and that was my issue. Especially since the manufacturer says this cam is recommended to be installed 4 degrees advanced... i was 8 degrees away from where I should have been. In my case I did buy a 9 keyway sprocket, however, Ive been told that's not necessary. If you know what you're doing, you can simply advance the teeth on the chains, just have to double check your work when you're done to confirm you are where you need to be with your adjustment.
> ...


So did TA performance send you a cam card telling you it should be installed 4 degrees advanced or did they just figure you were a mind reader? Did you degree it when you installed it? S#%&s that we have to do somebody else's job. I used to work in a wood moulding company way back, and would have to stop the moulders if it was spitting it out more than 1/32 bigger that spec. Well I got my cam etc from spotts. Gonna drop in a rebuilt distributor replacing one that has 50 plus years on it. And new wires. cap and rotor with brass terminals, and a new coil and nos points. Also bought a dizzy spring kit, just in case. Runs pretty good but all the parts I am replacing are about 12/13 years old. Time for a upgrade. See what happens. RM


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## gmjunkie (Jan 1, 2019)

TA sent a cam card recommending installation between 0 and 4 degrees advance, yet the cam was ground off and the engine builder I went to didnt bother to degree the cam, just installed it straight up.


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## RMTZ67 (Mar 12, 2011)

Lemans guy said:


> New rebuilt distributor will require you to find out what the centrifugal advance is on that one.
> 
> Since you are buying the curve kit, take off the two stiff springs that come with it and put on ONE medium silver spring from the kit.
> 
> ...


 Dropped in rebuilt distributor nw points dwell set to 32,new cap,rotor,wires and coil. All flamethrower brand. The springs that came with the distributor were heavy duty, so for now I installed the two black ones from the kit. I tried one silver spring but would not return the advance. So my initial timing is now 30* with the vacuum connected and 10* without. Why so much? Is this where the bushing comes in? How does that install? Thought I would get your opinions before I go any farther.Thanks


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## Lemans guy (Oct 14, 2014)

It means your vacumn advance can is giving 20 degrees advance real common, some give more but no good......

Remind me was this an HEI?


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## RMTZ67 (Mar 12, 2011)

Lemans guy said:


> It means your vacumn advance can is giving 20 degrees advance real common, some give more but no good......
> 
> Remind me was this an HEI?


 No points dist.


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## Lemans guy (Oct 14, 2014)

Ok, you need to change that vac can get a standard motor parts VC 181...Rock auto has em

O’Reilly has em under a borg Warner number BWD V375....same can....$15 or so

It pulls the lowest at 16 but that is still too much on today’s gas........

Email Lars, I gave you is email before and buy one of his vacumn correctors, about $14...he will mail it to you with instructions.

The vac can is easy to change, wait until you get both parts then put em in....another $30 bucks I know but the running difference is way better.

Get your Centrifugal the same way as before, one spring off vac plugged ,..run it til it stops advancing....subtract the base you had when you do this...

Then you will know if you need the bushing or not...it goes on a stem inside a slot under the center cam of the dist....

Don’t get too far ahead....find out your centrifugal advance number first....


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## RMTZ67 (Mar 12, 2011)

Lemans guy said:


> Ok, you need to change that vac can get a standard motor parts VC 181...Rock auto has em
> 
> O’Reilly has em under a borg Warner number BWD V375....same can....$15 or so
> 
> ...


Can I just put the one off my old distributor? I think it was pulling like 12 or 13. In a prior post


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## PontiacJim (Dec 29, 2012)

RMTZ67 said:


> Can I just put the one off my old distributor? I think it was pulling like 12 or 13. In a prior post


Should be able to, just compare them to make sure they are the same and will attach in the same manner. I'd give it a try and if it does not work, then go the other route.


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## Lemans guy (Oct 14, 2014)

Yes sure 12 or thirteen is good, do that, then check your centrifugal.....


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## RMTZ67 (Mar 12, 2011)

Lemans guy said:


> Yes sure 12 or thirteen is good, do that, then check your centrifugal.....


I swapped them and no change. Makes me question myself if I got them swapped.:banghead:Is it possible it has something to do with the distributor itself? If not I will stick my old dizzy with new? vacuum advance.


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## Lemans guy (Oct 14, 2014)

Well you may have your weights moving at idle speed adding some advance. Usually to weak springs do that or a very high idle speed.

Normal idle has range, but lots of these cars are 750 850 with stroked motors, factory idle 500, 600, 700..

But you said that you had strong springs, weights could be hanging up and adding timing. Read the number on your new vac can does it say 20? Often they are stamped with an advance number in crank degrees.

If the can reads 20 and adds 20....it is operating correctly but the wrong can to use.

Your old can and dizzy may be and sound like to me they are a mess,....I would stick with the rebuilt and use the can and corrector I suggested....you cannot make a car run better for that $30 spent anywhere

But remember the first thing is to find out your centrifigal advance in the rebuilt unit.....

Once you know it you will be able to tell if any centrifigal timing is coming in at idle.....and if your idle is way too high you have to turn it down


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## RMTZ67 (Mar 12, 2011)

Lemans guy said:


> Well you may have your weights moving at idle speed adding some advance. Usually to weak springs do that or a very high idle speed.
> 
> Normal idle has range, but lots of these cars are 750 850 with stroked motors, factory idle 500, 600, 700..
> 
> ...


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## PontiacJim (Dec 29, 2012)

OK, so now you are where you should be with the can swap. 10 degrees at idle with no vacuum, 20 degrees at idle with vacuum connected. Means the vacuum can gives you 10 degrees.

750 idle can be fine. You can tell by sound. An HP cam may need more idle than a stock cam.

Now check for total mechanical advance (vacuum disconnected) and at what RPM.


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## Lemans guy (Oct 14, 2014)

Right PJ,......good work RM........getting close.....


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## RMTZ67 (Mar 12, 2011)

Remind me again. Should I turn my timing light to let's say 45* and see at what degree it's all in, and at what rpm?


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## Lemans guy (Oct 14, 2014)

You will be testing for TOTAL centrifugal timing....forget RPM’s that where everyone gets confused

Rememmber to remove one spring so you reach mechanical limit quickly.......

The weights will only go so far...they stop, .....Steel hits steel....once they fully deploy.....if you just checked it to a certain RPM you will be way off as more timing will still be in there most likely......

Set your light up to a high number...say 40 so you are in range and zero it on the mark when it STOPS advancing

What you are looking for is when the strobe STOPS advancing....no matter if you rev more it won’t go more....you can read on the tape or the light.....

Forget RPM’s here.....

When you get that number subtract the base you had....like 10 for the centrifugal advance number.

Only now will RPM’s matter as you set springs for when that mechanical limit is reached...

By just reving it to 3000 is no good as your springs may not bring it all in until 4800...


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## RMTZ67 (Mar 12, 2011)

Lemans guy said:


> You will be testing for TOTAL centrifugal timing....forget RPM’s that where everyone gets confused
> 
> Rememmber to remove one spring so you reach mechanical limit quickly.......
> 
> ...


So I took off one spring vacuum plugged. And at 20* on the timing light it was at 0 on the timing cover.


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## Lemans guy (Oct 14, 2014)

When you remove one spring, it should idle at 10 degrees base......then watching with your light rev it up until the STOBE stops advancing..

Forget the RPM’s here it makes no difference.....

Rev it a few times and make sure you know where the advance STOPS.....turn it off, subtract your base 10 from that number and you will have your centrifugal advance number....

Then you can see what is next......that number is the “sine qua non”.....the essential element...


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## Lemans guy (Oct 14, 2014)

Use one or the other the tape reading advance or the light reading advance not both...

If you are idling at zero turn the distributor to 10 degrees advance....by the tape..your timing light set at 0......

That is 10 degrees advance now rev it with one spring and how high it goes on the tape...where does it stop going any further...

You should have no retarded timing below zero everything you are dealing with is Before TDC


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## Lemans guy (Oct 14, 2014)

Was your base set at 10 degrees advance when you began? If it was something is wrong if it was set at zero still seems low.....

Set your timing light to zero,..and just read the advance off the tape, set base at 10 on tape both springs on.

Now shut off car remove one spring, the only thing you want to see now is when it stops advancing,...rev it up until that happens a couple of times...a helper is good here , and parking brake and chock the wheels..

You have to aggressively rev the car up, but the particular RPM is not important here....try again and double check, you are close....


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## RMTZ67 (Mar 12, 2011)

Lemans guy said:


> Was your base set at 10 degrees advance when you began? If it was something is wrong if it was set at zero still seems low.....
> 
> Set your timing light to zero,..and just read the advance off the tape, set base at 10 on tape both springs on.
> 
> ...


 I think it moved before while revving because I did not tighten the dizzy enough. So I reset it @ 10* tightened down the dizzy, took one spring off and was able to get it to 35*. Both done with the vacuum plugged.


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## Lemans guy (Oct 14, 2014)

Perfect you have it now!

Your centrifigal advance is 25 degrees

Now set your base at 11 degrees......Total Timing will be 36 degrees ( vacumn is never considered a part of total timing

Reconnect your Vacumn advance, which is 10, plus the 11 base will give idle timing at 21. It will idle nice and cool there.

The only thing left is the springs, I would recommend one bronze and one silver, the black are too strong. 

This is where RPM’s now come in........You should get timing with those springs from about 1000 RPM to 3400 or so...

You thought the silver spring was too loose but as long as no timing from centrifugal is pulled in at idle 750 RPM....you are ok...

And now you will know if timing at idle goes over 21.....it is centrifigal coming too low and you have to adjust springs

Try the silver and bronze and drive it a week or two,...should run real good, if no pinging you could turn base up 2 degrees but you are getting in detonation territory, and if it pings at 36 turn the base back two degrees to 9 .....+25 will give you 34...

So great work you should feel it real strong with just a light pedal and a nice smooth acceleration thru the bands...

Great work!


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## PontiacJim (Dec 29, 2012)

RMTZ67 said:


> I think it moved before while revving because I did not tighten the dizzy enough. So I reset it @ 10* tightened down the dizzy, took one spring off and was able to get it to 35*. Both done with the vacuum plugged.


35 will work, but I might bump the 10 up to 12, and this will then bump the total up 2 degrees and give you 37.

So you are good as is, but you can play with it a little to fine tune.

Now that you have 35, the next step is to get your timing curve dialed in. This is where you play with the springs. Try to get the 35 all in around 3,000 RPM's. You can go 3,200 RPM's, but the closed chamber heads can take a little more advance and earlier curve BUT, you have to make sure no detonation or pinging under load.

So it'll be up to you to fine tune it if you want to play around with it. You may want to go with 10 degree initial, and 35 all in at 3,000 RPM's to get a baseline, take the car for a road test, and then adjust from there. Do this with vacuum disconnected on your tests. Hook vacuum up once you are happy with your mechanical timing. :thumbsup:


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## RMTZ67 (Mar 12, 2011)

PontiacJim said:


> 35 will work, but I might bump the 10 up to 12, and this will then bump the total up 2 degrees and give you 37.
> 
> So you are good as is, but you can play with it a little to fine tune.
> 
> ...


 Just for refresher.... My altitude is 5000' and I lowered my compression to 9.6:1. 91 octane here. I just checked rpms with current springs 35* @ 3500 rpm's


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## RMTZ67 (Mar 12, 2011)

Lemans guy said:


> Perfect you have it now!
> 
> Your centrifigal advance is 25 degrees
> 
> ...


 So I installed a bronze and silver and it went up to 35*. so should I now try two bronze then black and bronze etc until it stays at 21?


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## Lemans guy (Oct 14, 2014)

Your centrifigal timing is now limited to 25 degrees,...springs cannot make it go any higher......springs can only determine how fast that 25 is achieved

If your base is 10 degrees....that is 35....if you are getting 35 at 3500 RPM’s that is where you want to be.

I would set it at 11 base and grab 36 total......11 base + 25 Centrifugal = 36....

See when that is achieved 3500 RPm’ss or lower, leave it....

When you add 10 Degrees vacumn advance your light throttle cruise will be 46 .....perfect on today’s gas....


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## RMTZ67 (Mar 12, 2011)

Ok, so should I just put my original springs back on? Since the bronze/silver spring jumped my base timing up to 35. With the vacuum connected. Not sure if I made myself clear there. Thanks LG & PJ for your help.


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## RMTZ67 (Mar 12, 2011)

I'll reread your response. Maybe your answer was there. Thanks again. RM


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## Lemans guy (Oct 14, 2014)

Yes you could use the old springs.....bringing it all in by 3500 RPM

At 750 RPM idle you should only have 21...11 base and 10 from your vac can....

If more timing is coming in at 750RPm the springs are too light....

3500 RPM with all 36 degrees in is very good drive it and enjoy it.....!


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## Lemans guy (Oct 14, 2014)

With the bronze and silver you added 14 degrees of centrifigal timing...

to your already 21 degrees of idle timing...

That is what you do NOT what....centrrifugal timing should only come on when RPM’s increase....


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## PontiacJim (Dec 29, 2012)

RMTZ67 said:


> I'll reread your response. Maybe your answer was there. Thanks again. RM



I think you are confusing yourself. Forget about the vacuum advance for now.

Get you mechanical first - whatever that is.

If you are saying that your initial (BASE) jumps up from 10 degrees at 800 RPM's on the balancer to 35 degrees at 800 RPM's on the balancer when you hook up the vacuum advance, you have something very wrong.

If you have 10 degrees initial (BASE) at 800 RPM's and hook up the vacuum advance, you should see about 20 degrees initial (BASE) at 800-900 RPM's. Hooking up the vacuum may raise engine RPM's a little - then you adjust your idle down and idle mixture screws to dial in the engine's idle. 

This is why you set the initial (BASE) and total mechanical (DISTRIBUTOR ADVANCE WEIGHTS/SPRINGS + BASE) with vacuum plugged. Once you have that, then you can hook up the vacuum advance. You do not need to know what the total mechanical advance + vacuum advance is at 3,500 RPM's. Vacuum readings are seldom steady state as vacuum is a relationship to throttle position. An engine develops the most vacuum when the carb is closed (your foot off the gas pedal). An engine develops the least vacuum when the carb is wide open (your foot to the floor). Very seldom is the carb at a steady state as you are constantly adjusting your foot (the carb) as you drive down the road to give it gas, let off the gas, coast, etc..

The important number for the vacuum advance is at idle. This tells you how much vacuum advance your distributor has built into it. So without the vacuum advance connected, you have an initial (BASE) timing of 10 degrees at 800 RPM's. Then you connect your vacuum line, your initial (BASE) will jump up to 20 degrees at 800ish RPM's. This tells you you have 10 degrees of timing that the vacuum advance provides.

The additional vacuum advance has nothing to do with the total mechanical advance of 35 degrees @ 3,500 RPM's. The vacuum advance only fully kicks in when you let off the gas (highest engine vacuum). The purpose of this vacuum advance it to help in cooling down the engine and provide better gas mileage. BUT, if the engine is under light throttle, you won't get the full vacuum advance of 10 degrees, you may only get 6 degrees out of it because the throttle is partially open and not creating a full vacuum situation in the intake. Snap the gas pedal to the floor, you get 0 degrees of vacuum advance and rely soley on the mechanical advance and the curve you have set it at. So this is why you set your engine up without vacuum advance and then are simply supplementing the engine with vacuum advance as a means to start the engine easier at idle, and provide engine cooling & gas mileage once you are up and driving down the road. That's all the vacuum advance does.

You can remove the vacuum advance and it will not change how the engine performs. The factory/aftermarket dual point distributors from the "old days" did not have a vacuum advance. It would not work anyway because your foot is flat to the floor all the time and you would not build any vacuum to use it. If you had a race car, you would not have vacuum advance on it. So vacuum advance is not a "must have" thing, your engine will run just fine without it. But, for a street driven or street/strip car, it is better to have it for the reasons mention, namely engine cooling with regards to a Pontiac.

Hope that helps, but keep asking until you understand your engine's timing settings. :thumbsup:


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## RMTZ67 (Mar 12, 2011)

Copy that. I will put my original springs back on, with a 11 base timing and test it as PJ suggested with the vacuum disconnected and plugged. Maybe I can bump it up slightly from there because of the altitude here in NM. I will fine tune the timing while listening for detonation. Whew, Thanks again. RM


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## Lemans guy (Oct 14, 2014)

Exactly PJ.....you have it RJ,...just fine tune it now.....

With your vac advance hooked to full manifold vac you will get many advantages, and that ten degrees will be in there from idle through most of your driving cycle, it will drop out with the pedal down, but it depends on the specific can..

Basically what I am saying is you get more timing advance in a good way with the vac advance.....that will help with any leaner mixture at altitude...

I bet it runs good for you here and if you had Vac hooked to ported Vac before you will feel the difference....

Nice work!


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## RMTZ67 (Mar 12, 2011)

Hey guys, Thought I would update you on my adventure into my timing issue.Which maybe wasn't that big of issue, just not as skilled at timing issues as I thought. Back in the days I was happy if my cars just ran lol. But getting a 67 GTO changed my Perspective. So with the help of this forum and LG,PJ and bunch of other great guys with the willingness to share their expertise and opinion. I was able to rebuild my 400 and get my timing dialed in. Currently I have it set @ 36* total and it runs like a Gto should. I spoke with a guy the other day and he said he runs his cars around 41* total here because of the altitude here(5000). Don't think I am willing to go that far, but may try 38* and listen for pinging. Having learned some about total advance I am trying to dial in a 74 Camaro Z28 that I built to sell, but have kept while my goat was down. Let me tell you, it's not the torque monster this 400 w/ 3 speed dearborn with 3:55 gears is. It has a 350 4 bolt 4 speed w/ 3:73. After getting my Gto up and running again I am not sure about the 1406 edelbrock on the camaro, Gotta love those secondary's on the Quadrajets. I started my build on the thread "Cracked my 400 this what I found" 1 1/2 years later I am back on the road. Thanks again all. RM


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## PontiacJim (Dec 29, 2012)

Fanatastic! :thumbsup: Another success story and why this forum is the best. Very cool you have the Z28 to compare to the GTO. There is nothing like torque and that's the beauty of the Pontiac engine and why you want to focus your engine build on torque over horsepower.

The Q-jet is another thing of beauty. Nothing like the sound of those big secondaries popping open and that deep groan that comes out of the engine as it digs in. I just can't understand why anyone would want a Holley or EFI which just doesn't produce "that iconic sound." 

It'll be nothing but tire shredding and smiles from here on out. :yesnod:


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## integrity6987 (May 10, 2017)

PontiacJim said:


> Everything is correct, but might need some clarification - no offense *Lemans guy*. :grouphug:
> 
> Put the "0" degree of your timing tape where the lower line/mark is on your balancer - which is your TDC/0 degree position of the piston.
> 
> ...


Hi I hope you will share your knowledge and experience with me.
My car runs fine I don’t get any knocking but I’m trying to understand the engineering and design better; I'm a nerd 🤓

I was looking at the attachment from the 1968 service manual page 6E-25 (fig 6E-39)

Background: My car has the WS engine and is "stock"-ish. Base timing is 10 degrees w/ vacuum plugged. The engine has the stock distributor (pn 1111449) but when I rebuilt it, I installed advance springs that were only very slightly weaker than stock (compared using hanger/constant weight/measured deflection) I kept the stock weights. The centrifugal advance is “all in” 31 degrees at 2900 RPM.

It also has an adjustable vacuum advance can that is attached to manifold vacuum which is supplied with 12.5” Hg with hot idle set to 750 RPM. I adjusted the A/F and this is the most I can hold. As set, this adds 11 degrees. With the manifold vacuum applied my hot idle is 21 degrees.

So with that background – my question about the table.

The center section of the table lists the centrifugal advance specs.

I interpret these values to be added to base timing. This table lists 1-3 degrees at 700 RPM; 5-7 degrees at 1000 RPM; and 9-11 degrees at 2300; so at 2300 should have 19-21 degrees. (this matches with the way mine is set - I get 21 at that speed). And if I understand the table correctly there is a small contribution of the centrifugal advance factored into the base timing.

I’m not sure what the vacuum is at that higher sustained speed (I assume is less than the manifold vacuum at idle – PLEASE CONFIRM THIS ASSUMPTION –) and if the vacuum advance is adding anything at that higher speed.

In your high-speed shifting example when I take my foot off the throttle for the split-second - the manifold vacuum is restored? I never realized it would build so quickly! Is this lower (higher vacuum) than idle due to the increased flows?

The bottom part of the table lists full advance (of the stock module) of 10 degrees at 15-17” Hg.

Since my car is not making 15” (at idle) should I be looking for a vacuum leak?


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## PontiacJim (Dec 29, 2012)

integrity6987 said:


> Hi I hope you will share your knowledge and experience with me.
> My car runs fine I don’t get any knocking but I’m trying to understand the engineering and design better; I'm a nerd 🤓
> 
> I was looking at the attachment from the 1968 service manual page 6E-25 (fig 6E-39)
> ...


I was just helping another member with his timing/curve. Funny you cited all this because I was also using my '68 service manual for guidance. LOL Really bizzare.

If you note in the specs, the specs say "Dist. Deg." or Distributor Degrees. Distributor Degrees is 1/2 that of crank degrees. Correct? I had to look this up just to make sure I was not getting senile. Look at the vacuum advance numbers - pick one. It too says Dist.Deg., so at the Max Advance (Dist.Deg.) of 10, I read this to be 20 degrees at the crank. Am I wrong? So if you had 10 degrees of initial timing at the crank, then hooked up your vacuum advance to a direct/full manifold source, would you not get an idle setting of 10 degrees initial and an additional 20 degrees of vacuum advance if the manual states total vacuum advance is 10 degrees at 1/2 the crank timing?

Is the manual in error here, or am I losing it due to this Covid-19 virus???? LOL Help.


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## integrity6987 (May 10, 2017)

PontiacJim said:


> I was just helping another member with his timing/curve. Funny you cited all this because I was also using my '68 service manual for guidance. LOL Really bizzare.
> 
> If you note in the specs, the specs say "Dist. Deg." or Distributor Degrees. Distributor Degrees is 1/2 that of crank degrees. Correct? I had to look this up just to make sure I was not getting senile. Look at the vacuum advance numbers - pick one. It too says Dist.Deg., so at the Max Advance (Dist.Deg.) of 10, I read this to be 20 degrees at the crank. Am I wrong? So if you had 10 degrees of initial timing at the crank, then hooked up your vacuum advance to a direct/full manifold source, would you not get an idle setting of 10 degrees initial and an additional 20 degrees of vacuum advance if the manual states total vacuum advance is 10 degrees at 1/2 the crank timing?
> 
> Is the manual in error here, or am I losing it due to this Covid-19 virus???? LOL Help.


Ahhh! that explains some of it. After you pointed that out I found this.








 Distributor Advance and Crankshaft Advance Are Not the Same!


Ignition timing as read at the crank isn’t distributor advance. This gets confusing when putting a curve kit in the distributor.




www.hotrod.com





Still leaves me a bit puzzled about the manifold vacuum at various speeds...


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## Lemans guy (Oct 14, 2014)

Think of manifold vacumn as just the throttle plate’s degrees of opening.....

when it is closed the most...that is idle .......and the highest vacumn

when it is fully open...it is lowest vac, really no vac.......

it is just a line from idle to WOT...but since it is hooked to distributor at idle...you get all that timing...(10 extra degrees is what you want with today’s fuel)....at idle and when the throttle is mostly closed,...which is when you need more timing because you are firing a leaner mixture.....examples...idle and light throttle are leaner mixtures....more pedal pulls in more fuel for richer mixture and timing will properly start to drop from vacumn advance...

until WOT where no vacumn = no vacumn advance and your timing reverts to the proper total mechanical timing, which will be 32 to 40.......36 is usually the best start point.

ported Vac was an emissions fix to make the car run hotter at idle by retarding the timing and burning off noxious gas......Some may use it but the timing in my view is not as good.....

with ported vac you start to add timing as the throttle opens, once it reaches 10:degrees of timing they act the same, but you are setting up a vacumn curve to meet up with your centrifigal curve.

ported was for emissions,....I like the full manifold vac to the distributor with 10 degrees from the can,.....that way the timing from the vac can is a straight drop to WOT....andof course all the idle cooling benefits!


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## PontiacJim (Dec 29, 2012)

Lemans guy said:


> Think of manifold vacumn as just the throttle plate’s degrees of opening.....
> 
> when it is closed the most...that is idle .......and the highest vacumn
> 
> ...



OK, I got all that and was waiting for you to explain it.  BUT, what is up with the factory Service Manual which uses Distributor Degrees for the vacuum advance reading - which the book says is 10 degrees and what I thought it pulled, but Distributor Degrees is 1/2 of the crank degrees. Am I correct? So is the Service Manual in error and should actually state "Crankshaft Degrees" (or nothing at all) or should the advance number been only 5 Distributor Degrees?

I never really thought about this until I was helping another member and pulled out the manual. I knew we always went with 10 degrees of additional advance from the vacuum can, but when I read the fine print "Distributor Degrees," I started to question myself and had to smoke a few bowls of crack to get my mind cleared again. LOL So book error?


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## integrity6987 (May 10, 2017)

I don't think the manual is in error if you take distributor degrees and multiply that by 2 according to the ratio of crank degrees to distributor degrees it works out. It is essentially distributor degrees divided by (0.5)


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## PontiacJim (Dec 29, 2012)

integrity6987 said:


> I don't I don't think the manual is in error if you take distributor degrees and multiply that by 2 according to the ratio of crank degrees to distributor degrees it works out. It is essentially distributor degrees / 1/2


OK, then it is me seeing it backwards then? I will be honest, math equations, word problems, algebra, trig, etc., was never my strong point and the reason I did not go to a tech school to learn machining (which I would have liked to do) as I had to be honest with myself and with all the numbers in hundreds, thousounds, etc., I knew I would be more frustrated than enjoy it and that's when I got into trucking because I like driving.......so I just settle to hang around at machine shops and watch and ask questions without frying my brain. LOL


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## PontiacJim (Dec 29, 2012)

I mean just thinking about math would make my hair stand on end and look like I stuck my finger in a light socket. Its just some awful stuff.


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## PontiacJim (Dec 29, 2012)

OK, I kept thinking about this. Still felt something was incorrect. I pulled up the 1968 AMA specifications for the 1968 GTO distributor/timing specs. Then I compared these to the 1968 Pontiac Service Manual's GTO distributor/timing specs. Aha! I see a difference.

So the first attachment is the AMA specs. These are the distributor Model numbers they list for the GTO. The second attachment is the Service Manual specs. The same distributor Model numbers can be matched up with the Service Manual which are the last 2 on the right of the list.

The AMA spec use *Crankshaft Degrees *& a corresponding crank RPM throughout. If you look under "Vacuum advance, c/shaft degrees @ in. Hg nominal" it shows the maximum degrees to be 20 degrees @ 17-19 Hg for the #449 model, and 20 degrees @ 15-17 Hg for the #270 model.

The Service Manual specs use *Distributor Degrees* & a corresponding distributor RPM throughout. If you look under "Vacuum Control Model" it shows Maximum Advance to be 10 degrees @ 15-17 Hg for the #449 model, and 10 degrees @ 17-18.8 Hg for the #270 model.

Now correct me if I am wrong on this. (These specs are of course with the distributor vacuum disconnected) Using the AMA specs, the Initial timing is *9* degrees. The maximum Centrifigal (mechanical/distributor) advance is 18-*22* degrees @ 4,600 RPM. Total advance is typically listed in many books as 32 degrees which would be *9*+*22* = 31. Specs are not 100% accurate as there is a variable in all engines and these are base line numbers and you adjust from there. So using the AMA specs, we get what all of us know and use as 32 degrees for your total advance, but instead of 4,600 RPM's, many of us pull that down so as to get more performance out of the engine and I like to use 3,500 RPM's or even less. Then from there you can really get into adjusting your Initial timing at the balancer, your total mechanical timing (Initial + distributor weights), and then the RPM which the total mechanical timing is all in at. So a lot to play with and most of us use general recommendations from members and go from there.

In the AMA spec, note that the Vacuum Advance adds another 20 degrees @ 15-19 in. Hg depending on the vacuum can specs. If you throw a big lumpy cam with lots of overlap, your engine may not see 15 in. Hg, but rather 10 or 8. So a different vacuum can needs to be installed which there are several used in high performance cars of the 1960's that are made for such low engine vacuum numbers. Then you can also get aftermarket cans. 

The vacuum advance is only used at idle (if full manifold vacuum), part throttle/cruising mode and is dependent upon 2 things A) - the location of where the vacuum line is connected, either direct manifold vacuum or ported vacuum, B) the position of the throttle blades in the carburetor. You will see direct manifold as the source to be used and recommended on the forum. Ported vacuum can be used, and tried, but it generally does not give you what you want from the engine when they are modified for higher HP.

The throttle blades in the carb are constantly changing as you drive, thus the vacuum signal also changes. When you mash the gas pedal, those throttle blades are vertical and engine vacuum drops to near zero, so nearly no vacuum signal goes to the vacuum advance, the diaphragm in the vacuum can relaxes and that 20 degrees of advance provided drops to 0 and your engine is relying solely on the mechanical advance, in this case 32 degrees. As soon as you have beat that Chevy LS you were racing, you let off the gas (give the guy a middle finger and big grin) and the throttle blades close, and engine vacuum goes up and the vacuum can pulls in additional advance - up to 20 degrees more. The additional vacuum advance now aides in cooling down that hot engine that just whooped the LS guy, and it aides in increasing gas mileage - if there is such a thing with 500HP on tap. LOL So this is the real purpose and reason why it is always recommended to keep and use a vacuum advance.

When you build that engine, you may find that 20 degrees of vacuum advance is probably too much. The best sign is that the engine will have a surging sensation as you cruise down the road. But also, as you advance the initial timing as many do, you can over advance the engine's timing and experience weird engine conditions that you'll be scratching your head trying to solve. So if you were to advance your initial timing 6 degrees because that big cam likes it better and go from 9 degrees to 15, this would also advance your total timing the same amount, 6 degrees. So what was 32 degrees total timing is now 38 degrees. Your engine may like 15 degrees Initial timing better, but hate 38 degrees total mechanical and detonates/pings. Now add to that the full amount of advance you get from the vacuum advance when you are using part throttle/cruising, that 20 degrees plus your new total advance of 38 degrees puts you engine's maximum advance at 58 degrees.

58 degrees will most likely be too much and you will get that surging condition and even possibly poor running of the engine because it is over advanced. Once again, the recommendation from this forum is to use a vacuum can that provides 10-12 degrees advance putting your maximum total advance, Initial+Distributor+Vacuum, into a better and preferred range of 48-52 degrees. So the option is to get the correct vacuum can for your application that limits the vacuum advance, or make a stop within the distributor that limit the travel of the arm found on the vacuum can that pulls the advance plate in the distributor. These can be purchased or fabricated - the web has articles.

Same goes with the total mechanical advance. Remember we just said the engine loves the 15 degrees Initial timing but hates the 38 degrees? The amount of mechanical advance in the distributor can be limited by several methods. There is a bushing within it that deteriorates and then allows additional advance you may not want. A new bushing can be installed which most seem to find a piece of small plastic/rubber tubing and cut to fit. Aftermarket distributors often have the capabilities to adjust this with a series of different sized bushings you can insert and play with. So using one of these bushings could pull that 38 degrees back down to 32 and you are now good to go.

The other adjustment is the RPM that your total advance, Initial + Distributor, is all in. You just read that Pontiac sets this as 4,600 RPM's. Probably good for a street car and my guess is this also helped to protect the engine from detonation/pinging and thus warranty claims from engine damage. You will read how the "Bobcat" application in the mgazines had the total timing in at 2,500 and earlier to really pull power out of the engines. But, this was using the leaded race gas with higher octane and less prone to detonation. Again, you will see it recommeded from me that I shoot for a total around 3,500 RPM's when setting up the timing and you can adjust from there. Your engine might do well with total timing all in at 2,800 RPM's, or 4,000 RPM's. This can simply be a trial and error type adjustment. This change in total timing is done using different spring tensions that can be purchased in kit form and using a timing light, then go out on the road and test. Some will even change out/modify the weights in the distributor, but for the most part, the average guy will play around with the weight springs. We have covered swapping springs many times on the forum to improve performance and/or eliminate detonation/pinging provided that your engine's compression can be supported by the gas/octane you are putting in the tank.

What's the point of this long winded conversation? The factory Service Manual may be confusing with regards to engine timing specs as I found out when I used it as a reference. The specs are in Camshaft Degrees and 1/2 of what we typically speak of and use when working on out timing - even all the RPM numbers. The AMA specs are in Crankshaft Degrees and more in line with what most of us know and do when adjusting out the engine's timing.

Just for fun, I also included the AMA specs for the 1970 Olds W30 455CI option. Check out those specs. Now that is really nailing it down and not as generic as Pontiac's specs.

Hopefully I have not misspoken on any of this and confused anyone. I like most, am just a backyard hobbyist with no degree as a rocket scientist.


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## Lemans guy (Oct 14, 2014)

Yes you are right,....but what has changed dramatically from the manual until today is the gasoline!

most vac cans back then gave 20 plus crank degrees, some even more!...

it is way too much on today’s fuel and remember we are trying to make them run a little stronger on today’s fuel..

So for Vac advance we only want 10 degrees advance at the crank!...or 8 to 12 degrees at the crank....

guess what their is no vacumn can made that pulls only 10 degrees at the crank...the lowest pulls 16....that vac can pulls 8 degrees distributor....16 crank....we have to correct it with the stop to get 10.

also remember that timing on firing on todays gas is different....we still need to have more timing at leaner mixtures like idle and cruise.....less timing with the pedal down...

idle timing at 20 to 26.......or even 18 to 28.....will make your vehicle idle cool and smooth but you need to grab 10 degrees of that (at Crank) from Vacumn advance....

so 12 base....with 10 degrees Vacumn is a nice smooth 22 degree idle...cruise......is total 36 + 10 Vacumn....for 46.......that is on today's gas 

and for street performance all in say 2600 to 3600....I just set a Corvette 327 at 2800 all in but run good there even a bit lower.....I run my 461 at 3200 all in.

gas is different now ,...even pure gas is formulated different from the 60,s, many cars back then set base timing at 4 degrees.....then added 30 more from the centrifigal....and 20 more from vac.....

great for emissions.......


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## integrity6987 (May 10, 2017)

PontiacJim said:


> OK, I kept thinking about this. Still felt something was incorrect. I pulled up the 1968 AMA specifications for the 1968 GTO distributor/timing specs. Then I compared these to the 1968 Pontiac Service Manual's GTO distributor/timing specs. Aha! I see a difference.
> 
> So the first attachment is the AMA specs. These are the distributor Model numbers they list for the GTO. The second attachment is the Service Manual specs. The same distributor Model numbers can be matched up with the Service Manual which are the last 2 on the right of the list.
> 
> ...


Thanks!! That was an awesome exposition!!!!!


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## integrity6987 (May 10, 2017)

PontiacJim said:


> OK, I kept thinking about this. Still felt something was incorrect. I pulled up the 1968 AMA specifications for the 1968 GTO distributor/timing specs. Then I compared these to the 1968 Pontiac Service Manual's GTO distributor/timing specs. Aha! I see a difference.
> 
> So the first attachment is the AMA specs. These are the distributor Model numbers they list for the GTO. The second attachment is the Service Manual specs. The same distributor Model numbers can be matched up with the Service Manual which are the last 2 on the right of the list.
> 
> ...


So after I beat the LS dude and let off the throttle - that is when the maximum manifold vacuum is achieved. 
What I think would be happening is RPM coming down from 5000 to 3000 all the centrifugal advance is still applied and now with throttle blades closed the vacuum advance is making an added contribution both of these added to the base timing.




Lemans guy said:


> so 12 base....with 10 degrees Vacumn is a nice smooth 22 degree idle...cruise......is total 36 + 10 Vacumn....for 46.......that is on today's gas


I think I will have to hook up a vacuum pump to the vacuum advance can and see what it is able to provide as currently adjusted in the high RPM - throttle plates closed situation with its effect on the base timing at idle.
Next weekend....


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## Lemans guy (Oct 14, 2014)

The vacumn cans all come with a spec.....for example the B-1 vacumn can will start pulling timing at 8 -11 Hg. With Max advance of 8 degrees (Distributor) @ 16-18 Hg.

so it starts pulling timing at 8 Hg and is maxed out at 16 -18 Hg.....max is 8x2 = 16 degrees @ the crank.

if you know the spec and your timing thru the curve you can watch a Vacumn gauge in your cab and know how much timing you are pulling at any given vacumn reading.......The specs are very close, some will be 16 some 18,..likewise when it starts to pull 8 to 11 Hg...

you can check, but below 8 it will be zero. You can test an individual can to be more exact.

I set Vac cans at 8 to 12 degrees. Most wind up at 10 degrees. I can adjust the base 2degrees and sometimes the can.


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## Lemans guy (Oct 14, 2014)

Of course some guys like the adjustable vac cans. I don’t and remove them first thing on every distributor. I have a stack.

they only adjust the “rate” of vacumn and not the max the can will pull. Crane makes a vacumn stop plate, you can fabricate one, I use Lar’s corrector.

Nevertheless you can adjust the rate and make it work, but the can does not have a stop in it, I like it simple and reliable.


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