# Tri power / timing questions



## My65goat (Jul 26, 2017)

Hello all. I will start with saying that this is my first post. I have been reading much here and have found answers to some of my questions. There are many knowledgeable and helpful folks here.

So now my questions. First, do the harmonic balancers on these Pontiac spin ? To further detail my question, I have a 65 389 with the thin balancer. Do they have the rubber ring like the chevy? I know that the Chevy balancers have been known to spin and for that reason some just power time the engine rather than use a timing light.

And my next question. I recently installed a tri power setup and I am having a hard time getting the engine idle speed low enough to use my vacuum advance. I can only get the rpms down to 800 range with vacuum advance Un hooked but plugged.. If I hook the vacuum line up to the vacuum advance it speeds the engine rpms to nearly 1000 and I have no further way to lower the rpms ( idle screw backed out as far as possible and butterflies closed to max allowable) 

The only way I can get rpms any lower is to retard timing to a undesirable setting ( below 6° initial) or I can lean my idle screws but then I get a lean idle ( starts to get a lean miss at idle) .

I've talked to the carb builder many times and he recommended that I run the car with out using the vacuum advance. He claims that I simply will not get my idle rpms low enough with the vacuum advance pulling. 

Anyone else have similar experience? ?? Thanks in advance.


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## BearGFR (Aug 25, 2008)

Yes, Pontiac balancers are 2-piece and if you have any suspicion that the ring might have slipped, replace it. You don't want to take a chance on that outer ring coming completely off at rpm and dancing around in your engine compartment. It can do a ton of damage as you might suspect.

Tripowers can be difficult. Getting the throttle plates to align and seal can be a challenge. If there's any air at all leaking past the plates on your end carbs when they're supposed to be shut that will make everything off, and hard to manage. You might want to consider shipping it off to a shop that specializes in rebuilding them to make sure it's "right".
(Google is your friend)

Bear


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## Lemans guy (Oct 14, 2014)

Great points by bear on that carb.....on your timing, and vac advance as you add advance your idle will increase as you have found.

But the most likely problem you have is the Vac advance is pulling in wayyyy to much timing as they usually all do...When I pull those cans and test them on my distributor machine they often have 20 or 30 degrees of timing advance....way too much. Even the lowest pulling points Dist can pulls 16 degrees, still too much.....

You can read the can and look up the specs, or test it with your timing light hooked up and disconnected and you will see how much timing it pulls at idle....if it is more than 10 or 12 it is too much.

If you are running a points Dist, get a B26 Vac Can ......rock auto...SMP VC 181...NAPA calls it a VC 1808....

Then email [email protected] and get one his Vacumn correctors and knock that vac back to 10* and hook to full manifold Vacumn

If you are running HEI it is different.....But I gave you the points stuff because that is what the car came with and the tri power have little room for the big discs.

If you have already done this, than you need to work on the carb like Bear said , if not do this first then go to the carb....

Good Luck...You will get it!


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## My65goat (Jul 26, 2017)

Thanks for the replies. 
The reason I asked about the balancer was so I would know if I was getting my timing accurate with the light. After posting this I do believe that the balancer has Not spun. I set the timing at 0° with the light and I could hear some "woofs" out the exhaust indicating retarded timing, so I now believe the light.

And with the carbs, they are freshly rebuilt. I checked everything for vacuum leaks with wd40, no leaks. My next step was to remove and block off the secondary carbs and run the car on just the center carb. I still couldn't get the idle low enough for the vacuum advance. I spoke to the carb builder and he claims that I won't because the gasoline of today as compared with the gasoline back in 65. It does run pretty good but if I use my vacuum advance it idles to high for my liking. 
I have a new pertronix distributor with the latest version number 3 ignition. It does pull a ton of advance at idle. I will have to check how much. I believe that it was about 12° to 14° on top of my initial 6° or 8° to bring it to around 20° at idle. 

Maybe to much advance at idle???


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## Lemans guy (Oct 14, 2014)

20 at idle is perfect as long as it is 10 from vac and 10 from base.........close to that is what you want for smooth driving

26 more inside distributor..would make it 36...perfect


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## My65goat (Jul 26, 2017)

I will keep at it. I will get it one way or another. 
I did run it with the new tri power setup on the road. I ran it without the vacuum advance. Just plugged the hose. I have to say it didn't run bad.
That tri power sounds awesome, but it does bother me that I can't get it with the vacuum advance. 
What's your thoughts about running it without vacuum advance? ??


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## PontiacJim (Dec 29, 2012)

My65goat said:


> I will keep at it. I will get it one way or another.
> I did run it with the new tri power setup on the road. I ran it without the vacuum advance. Just plugged the hose. I have to say it didn't run bad.
> That tri power sounds awesome, but it does bother me that I can't get it with the vacuum advance.
> What's your thoughts about running it without vacuum advance? ??



You can run an engine without vacuum advance - many early factory HP cars typically had the dual points without vacuum advance and racers run their cars without vacuum advance.

I ran a 409CI with the factory Mallory dual point distributor and no vacuum advance -no issues. The key is to get the initial timing and advance curve set-up correctly for your engine application and this can mean a little trial and error work for you or taking it to a shop/guy with a distributor machine who can dial it in for you. Your gas mileage will drop a lot and your engine may run hot.

As BearGFR puts it, "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."


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## Lemans guy (Oct 14, 2014)

:nerd:wAll said is correct a as Vacumn advance hooked up and set correctly has no detrimental effect on full power or throttle down operations....

But that said, it has many advantages at light throttle and idle and overall response of the car in street driving as the advanced spark fires the light mixture early for strong power with barely touching the throttle,...responsiveness...

As an example,....take two cars, say with trans with no overdrive, 65 mph at 2800 RPM?..

The car with no vac advance under light throttle,..at cruise of 65 mph has 36 degrees of timing advance....it's top limit...

The car with vac advance under light throttle...at cruise of 65 has 46 degrees of timing advance.....it's top limit.....

If they both hammer down to increase speed..
....
..they both then have 36 degrees of timing advance.......you lose nothing for power but gain an increase to fire the lean mixtures at idle and light throttle......this make's your pedal very responsive..

Also, both of those cars at that 65 cruise have different throttle down applied angles, the car without vac will have to have the pedal down more.....because it needs more fuel to get the same speed......with 46 degrees of advance the lean mixture fires sooner and the applied throttle is very light.....less gas runs cooler with more advance, because it it more efficient.

My AFR meter, two widebands in each exhaust will show 14.3 to 14.7 AFR at that light throttle, on a carb.....14.7 is a complete burn of every gas molecule,..a perfect burn, all modern computers cars constantly change the fuel injectors and air flow to get that 14.7. they do it for emissions.....

Power comes at the 11.5 to 12.5 say AFR as you pedal down, a car with no vac advance would have a richer burn at cruise,...like 12.8 or 13 depends on the car.....or lower.

What happens when you set-up with no vac advance your timing is limited to 36 or 38... if you go higher you ping and knock,..

Vac advance let's you go with more timing, but none of the negatives effects. It also add idle cooling if hooked to full manifold vac...

It can be done many ways, racers have their purposes and know their cars,...some don't like it because they never had it set up right,...they had a vac can with too much advance so they declared them all bad...

My friends say "my car is running great", but when we pull the Dist it will have 65 degrees of advance from Base, cent and vac...so that is not possible,...it is just what they thought was great...

I am a Believer in Vac advance when set up correctly,....it loses you nothing and gains you more timing advance, more efficiently, better gas mileage, more responsive throttle, better engine cooling even at idle.....why would you give that up?

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


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## My65goat (Jul 26, 2017)

Great information. Yes, I do want to use the vacuum advance but just can't get the engine rims low enough. I'm getting pretty frustrated. ..


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## Lemans guy (Oct 14, 2014)

Check your throttle springs are they new and strong enough to pull throttle plates back to full close on end carbs?

Can you seal off end carbs and set base at 20 vac disconnected and plugged to engine?

Will it idle then at 750?


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## Lemans guy (Oct 14, 2014)

If so you have weak throttle springs or leak past those plates, you can seal the top of the carb with cardboard tape baggie....

Seal the two ends and keep end throttle plates tight and check


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## PontiacJim (Dec 29, 2012)

My65goat said:


> Great information. Yes, I do want to use the vacuum advance but just can't get the engine rims low enough. I'm getting pretty frustrated. ..


OK, we need a little more info. A few points that might be helpful.

Factory cam specs - same as the 1965 Tripower OR is the cam bigger OR somewhat deviated from stock, ie different LSA/lift/duration etc.. A cam that gets bigger may not idle at lower/factory specs - it may need to idle higher.

Automatic or 4-speed? If automatic, what stall is the torque converter?

What happens when you adjust your idle speed below 800 RPM's, does it simply die out?

Is the idle screw set on the lowest notch on the fast idle cam? Sometimes these can stick and not drop down as they should and your idle screw will be riding on the fast idle setting.

Do you have a vacuum gauge/tool to know what your engine vacuum is? 

Is the center carb stock? Is it possible that the set-up came from a car with a bigger cam and additional holes have been drilled into the throttle plates - a trick sometimes done to help idle on big engines with big cams.


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## My65goat (Jul 26, 2017)

Ok, more info. I just took the Carter afb off and installed a new tri power setup. It is the aluminum repo manifold with fresh built carbs. 
I have blocked off the end carbs and ran it on the center carb. I have the idle screw as far out as I can and it is on the proper cam as the choke is in proper position. The car has the 068 cam. It ran great with the afb. 
Again I have spoken with the carb builder many times. He does modify the carbs for today's fuel and tells me that I won't be able get the idle any lower because the fuel is not like it was in 65. 
I can get a reasonable idle rpm with the vacuum advance Un hooked and plugged but it is to high when it is pulling advance at idle. Around 750 Un hooked and speeds up to 950 with vacuum advance hooked up.
Oh yes it is a 4 speed car also. All factory specs. Cam and compression. 

I think I'm going to buy another center carb from a different builder. Can someone please recommend a really good place to buy a center carb. It is the 66 setup with the bigger center carb. 
Thank you all for your time.


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## Lemans guy (Oct 14, 2014)

When you add the vac advance at idle how much more timing does it add...

That is the key....most cans I see pull 15 20 or more....and it will run up your idle....

So try this before you go for a new carb. Set base,...vac removed and plugged, then connec tvac...how much more?


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## My65goat (Jul 26, 2017)

I'm going to have to check how much it pulls. I thought it was about 12° on top of my initial 8° but I will check it again tomorrow. I will get back to you. Thanks


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## My65goat (Jul 26, 2017)

Update. ..OK so for the last week I have been working on the tri power setup. I took off the secondary carbs and dag213 sealed the throttle blades for the best seal. 
I still have the same issue. The car runs and idles nice except I cannot use my vacuum advance. The lowest I can get the car to idle is about 700 rpms with the vacuum advance unhooked and plugged. When I hook up the vacuum advance it speeds the idle up to 900 rpms. I have no way to lower the idle rpms. (It's on the small idle cam and screw is backed out as far as I can).
Timing is at 6° at 700 rpms and I plug in vacuum advance and it pulls it to 18° and makes my idle higher than desired. 

Three brand new carbs ( fresh built). I'm thinking about trying a center carb from a different builder???? I could use some suggestions for a really good carb man please. Thanks

one last thought. ..I would probably be fine if it was ported vacuum. ....


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## My65goat (Jul 26, 2017)

Lemans guy said:


> When you add the vac advance at idle how much more timing does it add...
> 
> That is the key....most cans I see pull 15 20 or more....and it will run up your idle....
> 
> So try this before you go for a new carb. Set base,...vac removed and plugged, then connec tvac...how much more?


 the vacuum advance is pulling 12° of timing. It's perfect. ..but I still can't get my idle rpms below 900 with vacuum advance hooked up. ..


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## PontiacJim (Dec 29, 2012)

Wild guess, but you might take off the center carb to see if the butterflies are seating correctly. It is possible that during the rebuild they may have shifted just enough so that they do not close completely. I'd close the throttle plates and shine a light through to see if I saw light around the butterflies. If new bushings were installed in the carb base to tighten up the throttle shafts, maybe they are slightly off and causing the throttle plates not to close completely.

Again, just something to consider.


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## My65goat (Jul 26, 2017)

PontiacJim said:


> Wild guess, but you might take off the center carb to see if the butterflies are seating correctly. It is possible that during the rebuild they may have shifted just enough so that they do not close completely. I'd close the throttle plates and shine a light through to see if I saw light around the butterflies. If new bushings were installed in the carb base to tighten up the throttle shafts, maybe they are slightly off and causing the throttle plates not to close completely.
> 
> Again, just something to consider.


Yes, I rechecked the center carb this week. Butterfly were closing and I couldn't find any problems. It must be something in the way he builds these carbs because he keeps trying to convince me to run it with the vacuum advance Un hooked. I really want to be able to use the vacuum advance.


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## Lemans guy (Oct 14, 2014)

Yeah a carb with Dist not hooked to any advance should idle lower,.....unless your Dist weight springs are actually adding advance at 700, 800....

Make sure your Dist spring don't begin until after any idle speed. Light springs will pull advance in low and add to the timing. Also if you hook up the vac and have 18 degrees it will fire a leaner mixture......leaner than it will at 6 degrees...

Try adjusting the idle mixture when you have the vac connected,...I do that with my AFR ratio meter because that is where the car runs and can get it set perfect,....with 18 to 20 degrees advance you should expect about 750 RPM's.....

If that is not it then the idle air bleeds or idle restrictors etc depending on carb, will have to be adjusted....

See if that gets rid of lean misfire...


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## Lemans guy (Oct 14, 2014)

Just to explain,..if your Dist spring are real light and are adding advance when you are idling at say 700...the 6 degrees you are reading is not a true base number......

Your true number could be 0.... and the 6* could be added by the advance springs.......

Just make sure...you could pit the strong springs in just to test.....and make sure.


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## My65goat (Jul 26, 2017)

Thank you for your suggestions. I have not yet tried to adjust the carb with the vacuum advance hooked up. 

I have it running and idling nice. Just a fast idle rpm.

The distributor is a pertronix and is has the medium springs. I had the distributor in before I took off the AFB. I don't believe the springs are advancing at 700 to 900 but I could try the heavy ones just to see. 

I am about 99% happy with the tuning. The car is a absolute Animal with the tri power, timing appears really good , Plenty of power and NO pinging. So that's all good but I really would like to run my vacuum advance. 

I'll try to attach a little video of my test ride tonight.


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## My65goat (Jul 26, 2017)

Can't post the video clip. Here's a picture of the heart and lungs, LOL


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## Lemans guy (Oct 14, 2014)

I had a friends 64 corvette doing this same thing, would idle about 1000 RPM's has a lively cam...

we had set the curve on my Dist machine his carb was good, but the idle would not drop..

..so we pulled the distributor and measured the shaft end play, and usually I find on al the used distributors this is way to much. 

Mostly if it is not too bad you can get by with it,....... but his was about .".."...090 and it should be About .010.

So we shimmed the Dist dropped, the gap down to .010 and the idle settled down to 800 and did not fluctuate.

What happens is the sloppy Dist gear rides up just enough to advance the idle....if the timing mark is not rock solid that is an indicator of a gap too large.

You can buy Dist shims at any speed shop, jegs summit etc...use the hardened ones like Morosso. 

Remove the Dist and Just use a feeler gauge on top of the gear,...you will see usually one shim or two....that is where they go.

Worth checking.

Just a note that some hot cams it is hard to get that idle down.....


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## My65goat (Jul 26, 2017)

The distributor is only a few months old and like I said I had it in with the Carter afb 4 barrel and i had zero problems. I could set the idle down to around 600. It has the factory replacement 068 tri power cam. 

I am aware of what your talking about with a big cam that idles at 1000+ rims and sounds lopey still but that's not what I'm experiencing. What I have is a fast smooth idle when I hook up the vacuum advance. 

I can live with the idle I have with no vacuum advance. Just trying to get it proper. It bothers me that I have to keep the vacuum advance Un hooked. 

Like you said before, and something I had not yet tried is to adjust my carb with vacuum advance hooked up. I will try that tomorrow. Thanks


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## My65goat (Jul 26, 2017)

Another update if anyone is interested. I spoke with a very reputable Pontiac carb builder. He told me that most likely from the sounds of it, the idle tubes( I don't know the proper name) inside the carb are probably to small, so now I'm going to tear the center carb open and check it. The can be opened up with a very small index drill. I'll keep you posted. Thanks all


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## BearGFR (Aug 25, 2008)

Also.... are you running a bone stock camshaft or is it a little warmer than that?

Your vacuum numbers point towards it being stock, but I have to ask anyway. Reason: a warmer cam can require a wider than normal throttle opening at idle, and that can begin to uncover the transfer slots in the carb so that it's no longer running solely on the idle circuit.

If you haven't already, you might also make sure your idle mixture is right. Use a vacuum gauge (or better, an air/fuel meter but if you don't already have it set up for one that's more work and expense). Adjust for the highest vacuum reading you can get (or slightly lean.. around 15:1 air to fuel ratio). See if that helps any. I'd do that with the vacuum canister disconnected.

I'd try "everything else" before modifying the idle tubes. I'm not saying he's wrong, just be careful. It's pretty tough to "un-drill" those holes 

Bear


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## My65goat (Jul 26, 2017)

BearGFR said:


> Also.... are you running a bone stock camshaft or is it a little warmer than that?
> 
> Your vacuum numbers point towards it being stock, but I have to ask anyway. Reason: a warmer cam can require a wider than normal throttle opening at idle, and that can begin to uncover the transfer slots in the carb so that it's no longer running solely on the idle circuit.
> 
> ...


The cam is the 068 cam. The throttle blades are closed completely and even to the point where they stick because I'm not on the idle screw. The idle tube would be to small if they are not the correct ones. I spoke with John at Pontiac tri power and he has a list of what size they should be for several different applications. 
I explained to him what the problem is and he is almost sure that it's the idle tubes are to small. I should be getting the drill index tomorrow. I will know before I drill them by checking the size with the bit. 
I checked the engine vacuum while tuning and was getting around 15. 
I don't have a af meter but when I explained that the idle screws do very little change he was pretty sure it was the idle tube to small. 
I guess I will know tomorrow when I check.

He told me that it is a very common problem and that he sees quite often. 

We shall see. Bear thank you for your time and expertise. I have read many of your posts and have learned so much from all of you on here just by searching and reading posts.
I will keep you updated.


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## My65goat (Jul 26, 2017)

GOT IT!!!! Ok so I got my drill index on Wednesday and then took apart the center carb. The idle tubes where the 32 thousands that they were supposed to be for a stock 389. I then checked the throttle body idle screw hole size. I found them to be smaller than the specified 70 thosands. I called John at Pontiac tri Power to consult with him. He suggested that I open them up to specs but wasn't sure it would help. I put it back together and much to my surprise it helped but I was still not totally satisfied. I called John again today to tell him It helped. John suggested I should open up the idle tubes to 36 thousands which would be the specified size for the 421 engine. And much to my pleasure it did the trick. So now I have a nice idle rpm and have everything the way it is supposed to be, vacuum advance is hooked up with manifold vacuum without raving the engine rpms higher than desired. I'm so happy to have finally gotten this tri power setup ironed out. 
The only thing that upsets me is the fact that the carb builder wasn't able to get me on track. He only just kept trying to convince me to keep my vacuum advance Un hooked. 

A shout out to all for your help. And, also to the guys at Wrights tri power for their expertise. Thanks guys! !!


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## PontiacJim (Dec 29, 2012)

Success! :bannana: Thanks for the follow up as your frustrating experience will no doubt help someone else with a like situation.

It is really sad when you pay good money to a "carb" rebuilder/expert and they haven't enough experience or the knowledge to help you out or steer you in the direction that will solve your problem. Apparently you got a rebuilt carb from a person who can only rebuild and sell them and has no expertise in adjusting or getting them to run correctly - I guess he sells his carbs with his fingers crossed hoping they work.

Glad you found a rebuilder who really knows his stuff and could provide the technical advice that was needed to get your car up and running. Welcome to Pontiac Tripower | Pontiac Tripower


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## Lemans guy (Oct 14, 2014)

Great job, you stuck with it! ...now that will be a smooth running set-up....

Did your final idle RPM in drive come out about 750?...it will run nice and cool with that 20* advance at idle and you should have smooth of acceleration with a light pedal....try it,...!

Thanks for closing out the thread as Jim said so many folks don't and it will help someone down the line

Cool ride!


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## My65goat (Jul 26, 2017)

Lemans guy said:


> Great job, you stuck with it! ...now that will be a smooth running set-up....
> 
> Did your final idle RPM in drive come out about 750?...it will run nice and cool with that 20* advance at idle and you should have smooth of acceleration with a light pedal....try it,...!
> 
> ...


Yes! That's where I am, about 750 rpms, with 20° at idle, smooth acceleration and the best part is NICE Cool Water Temps at idle and driving. What a HUGE improvement on the water temps!

The only thing that I might change now is the vacuum advance limit to 10°

It is currently pulling 14° . So as of this moment I currently have 6` initial + 14° vacuum for 20° at idle. And total is 30° ( mechanical is advancing 24°).

If I can limit my vacuum to 10° Then I can bump up my initial to as much as 10°, then I would be at 34° total. And this would give me a little wiggle room for super fine tuning. 

I am going to call the carb builder this morning to let him know what I did to his carb to get it proper. And of course will follow up with the good fellows at Pontiac tri power. 

Thanks again all, I really appreciate your help, advice and support !!!!!!


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## BearGFR (Aug 25, 2008)

Very happy to hear that you've gotten that problem solved.

I've got very little hands-on experience with trip-power set ups, but I'll be sure to remember this one.

Bear


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## Lemans guy (Oct 14, 2014)

You should subtract your Centrifigal from 36 to get your base timing, 34 is ok,....but you can probably take 36 with no problems...some cars even take more.

Start at 36...and if no pinging leave it there. You set the base for 12.....12 + 24 = total timing....

Then add 10* from the vac at full manifold,.....your idle timing will be 22*... should run great there....and perfect light throttle cruise on today's gas 46*

Light pedal should give strong response!


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## My65goat (Jul 26, 2017)

Lemans guy said:


> You should subtract your Centrifigal from 36 to get your base timing, 34 is ok,....but you can probably take 36 with no problems...some cars even take more.
> 
> Start at 36...and if no pinging leave it there. You set the base for 12.....12 + 24 = total timing....
> 
> ...


I did have it up at 36° before the tri power, then I had the fast idle, so I was trying everything to get it to idle normal so I backed her down. 
Now that I have the carb situation straightened out I can ramp her up a little bit. 
I do have to be careful though, my 389 has the original high compression. 

I just found something great that the car loved! I went to the local race track and bought 5 gallons of sunoco "supreme blue 112" octane. 
I mixed one gallon of the race fuel to 4 gallons of sunoco 93 octane. The car runs great smells great. Seems like a good thing. 

I drove the car quite a bit last night. It really is running amazing. I can only imagine how much better I will be with my advance limiter and total timing back up to 36°..... just a little more "super tuning" and taking notes.


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## BearGFR (Aug 25, 2008)

If you really want to get your timing dialed in, work only off the total (with no vacuum) setting and do it at the track. It takes lots of time. Start "low" (around 32 degrees) and start making passes, being careful to make them as repeatable as you can (same conditions, techique, engine temps, etc) until you find the peak setting that yields the best times. ONce you find it, THEN read it at idle as if you're checking initial timing just so you can ID which initial setting translates to your best performance total, so that the next time you have a need to set timing you'll be able to work off the initial setting.

Bear


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