# 70 455 Engine Timing



## timmyg (Jan 2, 2012)

Hello
Been a good while since I have been on the forum. 
When it comes to Timing the Engine:
I have a freshly rebuilt "70" 455 HO Engine. Engine is bored 30 over. I have a "Summit" equivalent to a Ram Air Four Cam installed. I have a 66 Tripower setup on it as well. Turbo 400 Trans and 3.73 Rear End. I generally run 93 Octane Gas. 
My 455 seems to run well with the initial Timing set at approx 14-18 Degrees TDC. I have point ignition. The Vacuum Advance is unhooked at this point. Of course the Engine idles lower with the Vacuum advance unhooked but it also has a nice sound coming out of the pipes. If I hook the Vacuum Advance hose up, the Timing jumps up to somewhere between 28-32 degrees at idle. If I run the engine up to about 2500 RPM's the timing maxes out at about 44 degrees or so. This is sitting still with no load on the engine. Again, the engine seems to run and respond pretty good without the vacuum advance hooked up and has a better sound coming from the pipes. Meaning that it sort of rumbles a little rather than be smooth when I connect the vacuum advance up. When the vacuum advance is hooked up there is a sort of sputtering sound coming from the Tailpipes. Not a miss necessarily but sort of like a mild miss or sputtering sound if that makes sense. I have found when I disconnect the Vacuum Advance the sputtering goes away.
Couple of questions:
Do I need to utilize the Vacuum Advance or could I simply use the Base Timing along with the amount of advance I get with the centrifugal weights in the distributor? I do know that the engine tends to run cooler with the advance unit connected. Any advice is welcome as well as a possible answer to the sputtering sound I have when the vacuum advance is connected.
Thanks


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## PontiacJim (Dec 29, 2012)

Do a search through the forums. This has been covered many times. Read how to adjust the timing/vacuum advance as there may be one of the set-ups to fit your engine. Just went through this on an engine having "pinging" problems. :thumbsup:


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## timmyg (Jan 2, 2012)

How well can you hear pinging when it exists. I don't believe that I have ever really heard it in any of my engines. Maybe I have not had the issue before. I read a lot of articles where it talks about listening for pinging when adjusting the timing but if you have an exhaust that makes some noise I don't know how well you can hear it. ??


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## timmyg (Jan 2, 2012)

I was checking my Ignition Timing today and I tried to follow the procedure I read in the forum from Lars. This is what I came up with.
I disconnected the vacuum advance. I ran the engine speed up and the timing mark quit moving at about 3000 RPM's. So I reconnected the vacuum advance and set the Timing light to 38 degrees. I ran the engine up to 3000 RPM's and with the timing light set at 38 degrees I adjusted the distributor until my timing mark was on the zero mark. From what I have read I believe this should be very close to optimum Timing for my engine. I let the engine idle and checked the Timing with the vacuum advance still connected and the timing was about 22 degrees. With the engine idling I disconnected the vacuum advance and the engine did not want to idle and the timing mark was on the retarded side of Top Dead Center. I know that I have read that the initial timing is not all that important but I would think that being on the retarded side with vacuum advance disconnected means something is not right. 
Prior to all of this I had my initial Timing set at approx. 16-18 Degrees before Top Dead Center with Vacuum advance disconnected. With vacuum advance connected I had about 44-46 degrees advance all in at about 2500 RPM's. At this point I am not sure what is correct or what to do to get things right. I don't race the car, but I do occasionally hang foot in it and run up the road pretty good. I want to get the Timing correct to help the engine run its best and also eliminate any detonation. With the timing set as I just mentioned there has not been any Pinging that I am aware of. Any advice appreciated.


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## PontiacJim (Dec 29, 2012)

This is all with the vacuum advance disconnected and plugged. You want to have initial timing anywhere between 10-18 degrees depending on the gas octane/cam, and what setting allows the engine to turn over/start easily. 

Pinging is usually audible - a definite rattling sound when the engine is under load, but can be masked under loud exhaust/engine noise. 

Total timing really should not be much more than 32-38 and all in between 2500-3000 RPM's. Timing should begin to move from you initial setting at about 1,000 RPM's and continue up to the 2500-3000 RPM mark.

For example, if your initial timing is set at 14 degrees, you only want 24 degrees mechanical advance (distributor weights) to give you a maximum of 38 degrees total advance.

With your car, you say you have 14-18 degrees initial (no vacuum advance hooked up), which can be OK. Now you want to slowly increase the RPM's and see what the total advance is and at what RPM. I honestly can't tell you what your total advance should be, but I would shoot for about 36 degrees. So if your total advance goes beyond 36 degrees, then you need to limit the amount of mechanical advance in the distributor. There are aftermarket kits to do this which may include springs, weights, or pin stops. 

The vacuum advance, depending on what it is set for, will add additional advance which is typically about 14 degrees more. This only kicks in during light throttle or cruising to provide better gas mileage and help in engine cooling. It does not operate when you mash the gas or at low vacuum conditions.

With the RA IV cam, you may need a different setting on the vacuum advance as your engine vacuum will be lower than an engine using a smaller cam. There are aftermarket adjustable vacuum advance cans like Crane sells that you can dial in.


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## timmyg (Jan 2, 2012)

Before I read your reply I went out this morning with the car. All seemed fine at idle and cruising, however when I punched it from a rolling start the engine fell flat on its face and would not make hardly any power. This is still with the settings I had previously where as I had 38 degrees at 3000 RPM's with Vacuum advance connected. The engine started good like this. Once I returned home I rechecked and the settings were still the same. So I disconnected the vacuum advance and set the initial timing at 16 before top dead center at idle. Once I reconnected the vacuum advance the timing was about 32 degrees at idle.
If I am reading this correctly I have two options:
I can change the mechanical weights and springs to lower the amount of advance I get mechanically to an amount of advance when in combination with the vaccum advance connected and at 3000 RPM's I can keep the TOTAL advance at 36 or slightly below.
Or
I can keep the mechanical advance as is and keep the amount of mechanical advance that it produces. Then install an adjustable Vacuum Advance unit to allow me to adjust and or lower the amount of advance I get from the vacuum advance unit. Adjust the vacuum advance unit to produce the correct amount of advance needed so in combination with what the mechanical advance unit produces I will have no more than 36 degrees or so of advance at 300 RPM's. Is this correct.
Thanks for your help


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## PontiacJim (Dec 29, 2012)

Here are my thoughts on what you just said about your initial timing. Set at 16 without the vacuum advance hooked up. Then you hooked it up, and it jumped to 32 (which says your vacuum advance can is good for about 14 degrees of advance - which may be too much for your application). I am thinking that you have the vacuum hose going to a direct vacuum source, like off the back of the carb where the power brake hose comes off of, or its plumbed into the intake, or you have it on a non-ported fitting on your carb.

You want the vacuum advance line connected to a ported fitting - ie, the vacuum advance gets no vacuum at idle. It takes in its vacuum above the primary throttle blades which should be pretty close to closed at idle - so no vacuum is being made at the point where the vacuum advance port inside the carbs throttle bores picks up from. In this way, once you stab the gas, engine vacuum drops rendering the vacuum advance useless. When it does come in is when you have the carb partially opened during light throttle/cruisin' down the road just chillin'. Open the carb up for a little pick-me-up, engine vacuum drops, vacuum advance goes away/drops down. Back out of the carb to slow down or brake, primary throttle blades close, no vacuum gets above the closed blades, no vacuum until you once again ease into the carb to cruise - but if you stab it again to accelerate, engine vacuum drops, vacuum advance goes away.

The vacuum advance as you can see is in a constant motion in relation to the engine's throttle/vacuum when it is located at a ported fitting.

Now you can run without vacuum advance with no problems. Racers don't use vacuum advance. Most dual point distributors of old don't have a vacuum advance. Many new aftermarket distributors can either be had with or without vacuum advance. Vacuum advance only aids in better fuel mileage during light throttle/steady cruising and may aid in engine cooling. But with a 455 HO and RA IV cam/TH-400/3.73 gears gas mileage won't happen. So maybe simply disconnect the advance and forget about it.

The numbers you want to be concerned over are your initial settings at the crank ie your 16 degrees, and/plus the distributor's mechanical advance which gives you your total advance somewhere between 2500-3000 RPM's which should be somewhere in the ball park of 32-38 degrees. The distributor advance/weights will be a constant. It may be 22 or 24 degrees (unless your distributor is well worn). So figure out what it is. If you set your timing mark at 16 BTDC add 22 degrees distributor advance, you will have a total of 38 degrees. If you drop the timing mark down to 12 degrees add 22 degrees distributor advance, you will have a total of 34 degrees. The distributor/mechanical advance will produce/ max out for a total of 22 degrees each and every time the internal weights find their maximum centrifugal speed as they whip around inside the distributor - which means you will see a change in the RPM's at which total advance happens.

If you have 16 initial, plus 22 mechanical/distrib, for a total of 38 degrees coming all in at 3000 RPM's, then you drop the initial to 12 initial, plus 22 mechanical/distrib., giving you a new total advance of 34 degrees, the all-in RPM may now be lower at 2700 RPM's. So don't be surprised to see a different RPM at which total advance is obtained as you move your initial timing up or down on the balancer. This is where a stop is added inside the distributor to limit the weights total advance so your total advance does not get to high if your engine likes a lot of initial timing. For example, if the car runs good/fires up easy at 16 degrees BTDC and then you find out that your total advance is actually 42 degrees at 3,000 RPM's, you probably want to take at least 4 degrees out of the total advance to get your total more around 38 degrees. So there are several ways of limiting the mechanical weights inside the distributor from over advancing to include going to a lighter advance weight inside the distributor.

Again, I don't know your car/engine so I can't give you the specific numbers that your initial or total advance should be set at - this is something you will have to figure out. :thumbsup:


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## timmyg (Jan 2, 2012)

Thank you for a very good detailed explanation of engine timing and the vacuum advance function. I will try this out and see what happens.


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## PontiacJim (Dec 29, 2012)

timmyg said:


> Thank you for a very good detailed explanation of engine timing and the vacuum advance function. I will try this out and see what happens.


:thumbsup: Keep in mind that as you retard your intial timing, it may cause your engine to run hotter. Retarding timing makes an engine run hot. Advancing the timing makes the engine run cooler. The stock timing for the '71 455 HO is 12 degrees BTDC, the 1970 RAIV is 15 degrees so 16 is in the ball park.

I attached the distrib/timing specs from the 1968 Pontiac Service Manual just for example. You can see the dist. centrifugal degrees and vacuum advance degrees and their RPM's. *HOWEVER*, these numbers are in distributor degrees, not crank degrees, so multiply the numbers x2 to get your crankshaft/timing mark degrees.

Here is more info from out forums that you can soak up: 
http://www.gtoforum.com/f170/66-tri-power-timing-23953/

I help another member who has having timing issues/running rough at idle and this is the vacuum advance I found that was suggested on Chevy forums. DV1810 is the number, but Rock Auto has it using their number. He ordered it and told me it worked perfect and solved much of his problems. The can operates on lower vacuum engines (those with bigger cams). The DV-1810 should be all in by 8" hg and add up to 16 degrees crank timing @idle on *manifold vac*, they have a low starting point of about 3" hg. It might be cheap enough to give it a try and see what happens?

AIRTEX / WELLS 4V1053 Distributor Vacuum Advance | RockAuto

Also, here is the Crane adjustable vacuum advance kit with springs to recurve your ponits distrib. The PDF might give you a little info as well.
https://www.jegs.com/InstallationInstructions/200/270/270-99601-1.pdf


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## timmyg (Jan 2, 2012)

I apologize but I am still confused. In your above explanation you have said "You want the vacuum advance line connected to a ported fitting - ie, the vacuum advance gets no vacuum at idle." But then in the most recent reply you have said "The DV-1810 should be all in by 8" hg and add up to 16 degrees crank timing @idle on manifold vac. Also the link I went to that you attached has everyone talking about vacuum advance being utilized and having an impact at idle speed. I am really appreciative of the advice but I am still thinking that I am seeing conflicting information regarding vacuum advance and it being utilized at idle speed and affecting idle speed timing. Maybe I am just not interpreting this correctly.
Thanks


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## timmyg (Jan 2, 2012)

I have the Tripower and I do not have any ported fittings on any of the carburetors for the vacuum advance to be connected to. There is only one fitting on the center carburetor which is below the throttle blades which I use for trans modulator and choke. The Front carburetor has the one fitting in the back for power brakes but it is also below the throttle blades (Primary Vacuum). Any ideas on what I can do? With Vacuum advance disconnected engine already showing that it is running warm on 58 degree day.


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## Lemans guy (Oct 14, 2014)

Timmy you are on the right track and Pontiac Jim gave you solid info as usual..... let me build on your discussion 

the first number you want to find is the centrifigal advance number, ....we can almost guess it at about 16-18 from what you said. but here is how to get it......

disconnect your vac advance, and plug the engine vac side....set the base timing where it starts.

now run the timing up with your light and see where it stops, subtract the base timing. That is your centrifigal advamve.

now if that number is 18.......your base timing should be added to it to get total timing....18 +18 + 36......

now to vac advance...you want it absolutely and hooked to full manifold vac....you can use the B28 vac can PJ recommends, sometimes hard to find or get a B26 Vac can....

rock auto calls it a SMP VC 181,...NAPA calls it a VC 1808,,,O'Reilly calls it...a BWD V375....

Then email [email protected] and get one of his vacumn correctors for either can. Don't use the B26 can without the corrector, the B26 will be a little better and could be used but still too much advance.

the B26 or B28 and Lars corrector will knock your vac advance back to 10 *

Your hot cam can take more advance at idle as you discovered, so 18 base and 10 vac will be close for good idle cooling and street driving.....

Hook it to full manifold, you will give up idle cooling without it and 44 degrees is too much advance.

you want 46 to 48 on todays gas.

also adjustable vac cans only limit vac not total vac advance,,,,so somewhat tricky unless you have a vac limiter....like cranes or MSD.....

try this way, and you will be close......and good Luck!

:nerd::nerd::nerd::nerd::nerd::nerd::nerd:


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## BearGFR (Aug 25, 2008)

Timmy,
All timing settings for performance are to be done with the vacuum advance disconnected and plugged - period. Think about it --- when you're at wide open throttle and pulling hard, the engine is making almost zero manifold vacuum, which means under those conditions your vacuum advance will be doing nothing.

The purpose of the vacuum advance is to add ADDITIONAL advance under light throttle, light load conditions only. This helps with both fuel economy and with engine cooling. For power, it is never a factor.

The reason you always adjust timing with it disconnected is because it's impossible to duplicate the conditions of the engine running at WOT under load while it's sitting still in neutral in your driveway.

Use the search tool here to find all the other discussions about timing, optimum timing, and how to arrive at it. I know I've written about it several times here myself.

Bear


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## Huffman Hot Rods (Aug 23, 2021)

PontiacJim said:


> Here are my thoughts on what you just said about your initial timing. Set at 16 without the vacuum advance hooked up. Then you hooked it up, and it jumped to 32 (which says your vacuum advance can is good for about 14 degrees of advance - which may be too much for your application). I am thinking that you have the vacuum hose going to a direct vacuum source, like off the back of the carb where the power brake hose comes off of, or its plumbed into the intake, or you have it on a non-ported fitting on your carb.
> 
> You want the vacuum advance line connected to a ported fitting - ie, the vacuum advance gets no vacuum at idle. It takes in its vacuum above the primary throttle blades which should be pretty close to closed at idle - so no vacuum is being made at the point where the vacuum advance port inside the carbs throttle bores picks up from. In this way, once you stab the gas, engine vacuum drops rendering the vacuum advance useless. When it does come in is when you have the carb partially opened during light throttle/cruisin' down the road just chillin'. Open the carb up for a little pick-me-up, engine vacuum drops, vacuum advance goes away/drops down. Back out of the carb to slow down or brake, primary throttle blades close, no vacuum gets above the closed blades, no vacuum until you once again ease into the carb to cruise - but if you stab it again to accelerate, engine vacuum drops, vacuum advance goes away.
> 
> ...


I have a pretty fresh 455 that really runs good at around 16 degrees initial advance. Idles good, response is fantastic no pinging even when hot. Seems to run around 195 to 200 degrees while cruising or at idle on a 90+ degree day. Problem is at highway speeds (70 mph or so) engine starts getting hot (225/230 degrees) and doesn't want to cool off. My total "all in" timing is about 42 degrees. Could this be my problem? Should I limit the "all-in" to 38 degrees? I have a good clean radiator, good water pump, shroud that covers the entire radiator and a high efficiency Deralle electric fan and am running 70/30 (70 water/30 antifreeze) solution. Big amp alternator with plenty of voltage to the fan motor.


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## michaelfind (Dec 14, 2018)

What gears are you running? What rpm are you turning at 70 mph?


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## Huffman Hot Rods (Aug 23, 2021)

michaelfind said:


> What gears are you running? What rpm are you turning at 70 mph?


Not sure what gears, but a 2004R overdrive trans. At 70mph I would estimate 2000 rpm give or take 100.


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## Huffman Hot Rods (Aug 23, 2021)

Huffman Hot Rods said:


> Not sure what gears, but a 2004R overdrive trans. At 70mph I would estimate 2000 rpm give or take 100.


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## Lemans guy (Oct 14, 2014)

Yes if you are accuarately describing that 42 degrees of total timing, you are likely causing detonation, which causes heat, and heat causes detonation and it is engine destroying.

You need to back that timing off. You need to start by knowing what your Centrifigal timing is, it then determines what your initial or base can be. If you have 16 and 42…then you have 36 degrees Centrifigal timing……way way too much.

what kind of distributor are you running? HEI? Original style with external coil? MSD? Petronix? Etc,etc….


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## BearGFR (Aug 25, 2008)

42 degrees, if that's all mechanical (without the vacuum can) is a TON of timing unless you're running early, closed chamber heads like the 670's. Even with those, that's a lot. I'd back it off to 36 or even 35 total and see how it likes that.

BUT, just to clarify --- when I said 35-36 total, that means total -mechanical-, as in with the vacuum canister disconnected. If that 42 figure you quoted is WITH the can, then your overheating problem could easily be caused by not having ENOUGH advance at cruise. The details matter.

Bear


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## PontiacJim (Dec 29, 2012)

Huffman Hot Rods said:


> I have a pretty fresh 455 that really runs good at around 16 degrees initial advance. Idles good, response is fantastic no pinging even when hot. Seems to run around 195 to 200 degrees while cruising or at idle on a 90+ degree day. Problem is at highway speeds (70 mph or so) engine starts getting hot (225/230 degrees) and doesn't want to cool off. My total "all in" timing is about 42 degrees. Could this be my problem? Should I limit the "all-in" to 38 degrees? I have a good clean radiator, good water pump, shroud that covers the entire radiator and a high efficiency Deralle electric fan and am running 70/30 (70 water/30 antifreeze) solution. Big amp alternator with plenty of voltage to the fan motor.


As pointed out, 42 degrees total, if correct, is much too much.

What heads? Aluminum or iron??

Do you have a new harmonic balancer? If original, the outer rings can slip as the rubber bond deteriorates and can then give you a false reading on your timing. A new balancer should be installed and they can be had for around $100 aftermarket.

Temps look OK for cruising, but we always suggest to get one of the hand held laser temp guns to verify before "assuming" and trusting a gauge. Sometimes they lie and then you make a few changes hoping to fix things and it doesn't, but the fix was getting a correct/matching temp sensor or rebuilding the factory gauge. It also makes a difference where you place the temp sensor as most will have the sensor in th water crossover on the intake, but some do have the sensor on the side, near the forward area, of the head. If in the head, the temp will typically show hotter. So always a good idea to get then hand held laser gun to shoot various areas of the radiator to confirm that no part of it is blocked with junk, measure top hose and bottom hose and there should be a very noticeable difference in the 2 temps - because a working radiator will cool down the coolant at its bottom section going back into the engine. You can also shoot each head at various spots looking for any noticeable hot spots.

Do you have a 16 lb radiator cap?

Since the temps go up at higher speed:

1. - What RPM is "all-in" mean? 2,500, 2,800, 3,000, 3,500 RPM's?
2. - If the balancer is correct, 36-38 for iron heads would be better.
3. - Are you using a vacuum advance?
3.5 -What temp is the T-stat you are running? 160, 180, 195?
4. - Depending on fan type/shape, some of them can actually impede flow at higher speeds and this may be what is happening, Good at lower speeds, no good at higher speeds because the blades are blocking air flow. The shroud can also be a problem if it is not designed correctly. 
5. - Radiator, stock or aftermarket aluminum? Bigger cubes/HP/TQ will want a larger/better radiator and stock may not cut it.
6. -What RPM at 70 MPH?
7. -Trans cooler? If so, is it mounted on the front of the radiator blocking air flow? You do not want it on the front of the radiator if you have one.
8. -How many miles on the engine? A new engine is still "tight" and can put out a little more heat until things loosen up a little.
9. -Spring inside the lower radiator hose to keep it from collapsing? The lower hose can collapse and block water flow.
10. -Have you tried running the heater full blast to see if this cools the engine down any? The heater core can act as an additional radiator and if the engine temps drop at all, means the radiator is not large enough.

So get back to us with some answers to the above and we can narrow the problem down a bit more.


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## Huffman Hot Rods (Aug 23, 2021)

I went back and re-checked my numbers....static is set at 16 degrees. Centrifugal ads 10 degrees at 2500 rpm. That means a "all in" advance would be 26 degrees without the vacuum advance hooked up. Vacuum ads 28 degrees when I connect to a vacuum pump.

Keep in mind I have a 2004-R overdrive trans and at 70 mph the rpms are about 2000. This engine has 6X iron heads, low compression so I don't have to run race fuel. So much torque that I barely have the throttle open at 70 mph. Stock Delco distributor, ceramic coated stock exhaust manifolds. Stock desert cooler radiator (this is a 1957 Safari Station Wagon), radiator, water pump, hoses, etc. are as new. Hoses do not collapse. Radiator cap is 16 lbs.

Engine was professionally built by a Pontiac mechanic that had built several engines for the original builder of this project (the owner raced Pontiacs for many years) and has about 2500 miles or less on it. I would ask for his advice, but he died some time ago. The wagon is from Michigan and the owner didn't get to drive it much before he died in a boating accident.

I have a laser pointer thermometer and have added a dual gauge (digital and analog) laser temp sensor and gauge read within a couple of degrees of each other.

Trans cooler is built into the radiator, but I added a separate cooler mounted to the frame. Running 70/30 (70% water, 30% anti-freeze). Running heater full blast doesn't do much when it gets hot.

Besides the Full shroud Derale puller fan assembly there is a pusher fan to help with the air conditioner condenser. No I am NOT running the air conditioner during all of this.

My thoughts are that at 70mph the throttle is open so little that the vacuum advance is still advancing. That could put my "all in" at around 54 degrees worst case if I'm understanding all of this.

If I were to keep the vacuum advance disconnected could that solve my problem? I have not checked to see if there is any advance limiters on the centrifugal advance yet. I don't know how much a stock distributor is set to advance.

I hope I've given enough info for someone to give me advice.

Thanks


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## Lemans guy (Oct 14, 2014)

Nice set up sounds awesome. But let’s help you clarify your timing. Don’t get confused by this “all in” talk at 2500 or 3000 or whatever. That “all in” is the last number to get in your timing equation.

You have to first know what your Centrifigal advance is,…it reaches a mechanical stop based on how far the metal weights can travel. If you know it at 2500 it does not tell the whole story,..is there more? How much?…..

it is the first number you need to know. So pop the dist cap take off the rotor and remove one spring. Put the rotor and cap back and hook up your advance timing light. Now run the Rpm’s up in park or neutral and see when the timing “stops” advancing. Note that number. Then subtract your base timing, you had 16. The weights will reach full mechanicalmstop very fast with one spring off so you won’t have to rev it too high.

now you know what your Centrifigal is and base can be set accordingly and proper vacumn advance added. At light throttle on today’s gas with a properly set up vac advance your timing should be 46 to 48 with 10 from vacumnnincluded.


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## Lemans guy (Oct 14, 2014)

And don’t forget to replace that spring!


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## Huffman Hot Rods (Aug 23, 2021)

Thanks, I'll pop the distributor and have a look for any limiter stops. The centrifugal gets a max of 10 degrees no mater how high the is revved. That doesn't seem like much, but I don't know what a stock one is set at.

I'm thinking maybe an adjustable vac advance unit or some type of stop might work.


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## PontiacJim (Dec 29, 2012)

Huffman Hot Rods said:


> Thanks, I'll pop the distributor and have a look for any limiter stops. The centrifugal gets a max of 10 degrees no mater how high the is revved. That doesn't seem like much, but I don't know what a stock one is set at.
> 
> I'm thinking maybe an adjustable vac advance unit or some type of stop might work.


Great color combo on the Safari. Looks like the color ad for the 1956 Pontiac convertible which was that rose with black as I recall - one of my favorites. I had a '57 2 Dr in my youth but junked it as it was very rusty - but today would have been a good candidate to save, times change.

Is this a big cap HEI distributor - kinda sounds like it with the numbers you have for the advance. If so, a little different in setting them up versus points. If you have an HEI, here is an article you might want to read that explains a few things and making adjustments.





__





Changing the Advance Curve on HEI Distributors






pontiacstreetperformance.com





Focus on your Initial (at the balancer) and then Total with the mechanical (weights in distributor). Don't bring in the vacuum aspect until you get these straight first as you may only confuse yourself.

You may have a stop/limiter bushing in the distributor, or some really strong springs that can also limit the advance. Make sure the weights are free to move and not stuck or rusty and preventing movement.

You may want to bump up the Initial a little more. The key is starting. If the timing is too far advanced on the Initial, the starter/engine will labor to turn over. 

But do as* Lemans guy* advised and get your mechanical numbers as he suggested and see if there is anything like a limiter being used.


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## Huffman Hot Rods (Aug 23, 2021)

Thanks Jim,

have a gear reduction starter and have never had any problems turning the engine over even when hot. If I go much more than the 16 degrees I have initial, I can hear that it takes a little more to turn it over. At the 16 it even starts easy by just turning the key (no throttle). 

I'll have a look at the distributor. Yes it's the large cap HEI.

Appreciate your input.


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## Lemans guy (Oct 14, 2014)

Huff, your original post said “stock Delco Distributor” , now saying HEI. Just note if HEI meaning coil in top of cap on distributor with wide body……don’t use the one spring method, just use 2 light springs to test.

An original distributor, prior to 1975 would be a “points” style with a narrow body and a separate coil.


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## Lemans guy (Oct 14, 2014)

I have seen lots of those HEI with real stiff springs and all the timing won’t come in until 4500 or 4800 RPM’s. 10 is awful low for total Centrifigal advance. If the builder set base at 16 I would expect that number to be more like 18 or 20 degrees for 34 or 36 total. Try 2 light springs and retest. You need to be sure of those numbers.


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