# 66 Tri Power Timing



## Bayoupappy (Sep 22, 2009)

I have a 66 tri power which I think is all stock. I can't get it to idle decent at 6 BTDC with vacuum advance disconnected, I have to go to 10 BTDC. With the vacuum advance connected it jumps to 30 BTDC and when I rev it to get the centrifugal advance it goe to 42 BTDC. Does this sound right to anyone. It runs good at this setting, but I'm thinking the 42 BTDC is too much. Any thoughts???


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## Rukee (Feb 8, 2007)

I run my `65 tri-power 389 @ 32* total advance. You won't get anymore power over 36*, but I get some pinging at 36* so I back it down to 32*.


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## geeteeohguy (Feb 2, 2008)

Do what Rukee says. Set the timing at 6 degrees with the hose disconnected. Doesn't matter if it idles cruddy with it disconnected...you're going to reconnect it after you're done seting the timing. Pontiacs don't like more than 36 degrees total, even 36 is tough with stock compression and pump gas these days. Don't overthink the whole thing. Set it at 6 BTDC, and run with it. If it pings, take it back 2 degrees at a time until it doesn't. You may have to reset your curb idle speed and mixture after you do this to get the idle quality back to snuff.


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## Rukee (Feb 8, 2007)

I set the timing with the hose on, rpm's about 3-3500. Set to 32* and let the timing do what it wants at idle.


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## geeteeohguy (Feb 2, 2008)

Yeah, I know what you do, Rukee...but your a bonafide auto techinician. You can "wing it" and pull it off (except when your welding glass!). Most folks don't have the "seat of the pants" ability to dial in an engine. By the book is the safest way for the folks that don't have 30 wt in their veins.....


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## Bayoupappy (Sep 22, 2009)

Thanks, I checked it again today before I saw your replies. It's 8 at idle, 26 with hose connected and it maxes out at 40 @ 3500 rpm. I'll back it down to 6 at idle and see what it does but it seems the vaccuum advance is a little too aggressive, bumping it up 18...
Thanks again.


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## 646904GTO (Feb 10, 2008)

You need to restrict the movement of the vacuum advance pod in the distributer. This can be easily acheived by removing it and apply a small weld (or a tiny nut and bolt) in the slot to limit the advance travel. It can be adjusted with more weld or a file. In cases where you are really close just adjust the base timing a little to achieve 34 total at the crankshaft. You will eliminate pinging and have a crisper throttle response.:seeya:


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## geeteeohguy (Feb 2, 2008)

You don't need to do anything with the vacuum advance pod on the distributor, since it does not have any real affect on the total advance. On this set up, it's connected to manifold vacuum, not ported. When you open the throttle, especially wide open, you loose manifold vacuum. Goes to 0. No vacuum advance. The mechanical advance is what gives you total advance on these cars at RPM. The vacuum advance is ONLY there to help the car run cooler at idle, and improve off-idle driveability.


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## Rukee (Feb 8, 2007)

It's more like a Vacuum retard.


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## kisertl (Nov 9, 2009)

My thoughts on this is you have something else going on, make sure your front and rear carbs are shut at itel and not sucking air, do a vacuum leak test on the carbs using a propane bottle with a hose attached could be warn throttle shaft bushings. look at your distributor for any signs of wear. old centrifigal advance springs can cause problems at idel and max advance, advace weights could be hanging up. My 66 tripowe is like a rock at 6 degs and total advance is 32 at 3k rpm. runs great. Don't get tunnel vision on timing, be open to everthing.


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## 646904GTO (Feb 10, 2008)

Bayoupappy said:


> I have a 66 tri power which I think is all stock. I can't get it to idle decent at 6 BTDC with vacuum advance disconnected, I have to go to 10 BTDC. With the vacuum advance connected it jumps to 30 BTDC and when I rev it to get the centrifugal advance it goe to 42 BTDC. Does this sound right to anyone. It runs good at this setting, but I'm thinking the 42 BTDC is too much. Any thoughts???


Hmm...timing jumps 20 degrees with the vacuum advance attached and 10 degrees with RPM...."you don't have to do anything with the vacuum advance pod on the distributer, since it does not have any real effect on the total advance" ??


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## yammiman (Apr 19, 2009)

I would say you need to check both your mechanical advance and you vacuum advance - check the initial timing at idle with the vacuum unhooked then check the total timing with the motor reved to 2500 to 3000 (mechanical should be all in by then) - if you have 6 degrees initial and 36 degress total, there is 30 degress of mechanical advance - if it idles rough, you can change the weights in the top of distributor for less mechanical advance - if the car runs/starts better with 8-10 degrees of initial timing, that is what you are going to want to do - once you get your initial and mechanical timing where it needs to be, plug the vacuum back in and go for a ride - get up to cruising speed and look for a small grade to go up and listen for any spark knock - if you get spark knock you need to decrease the amount of vacuum advance - you can buy different vacuum cans that have different amount of advance or you could get an aftermarket adjustable can - you must get your timing where it needs to be before you do any adjusting on the carbs because your initial timing effects your manifold vacuum - you can actually set your initial timing with a vacuum gauge hooked up and shoot for the highest amount of vacuum you can get at idle - timing is the starting point of any tune up!!


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## Hammer (Aug 12, 2007)

*ported vacuum*

there should be one spot on one of the carbs that will give you no vacuum at idle,,it's been so long on mine and i run a Mallory DP(no vacuum),but,,all the chivy motors i've ran there would usually be a correct port and awrong one(at least!,specially as we got `newer' and newer junkyard stuff with more ports to block off),it shouldn't have any vacuum at idle then increase as the R's go up,i'm certain you can find`correct' specs for vacuum cans,dif motors, cam, carbs HAD dif spec'd vacuum,at least back then,,you could have the dist curved but if it's getting all that vacuum right away `curving' is pointless(hey now theres a PUN):lol:

late 70's Cadillacs with the 425 motors had the vacuum maxed like that to pass the tailpipe sniffer DEQ tests(at that time),like21 degrees lead?,torque galore off the bottom,fall on it's face pulling out on the interstate slow roll on,,if you worked at it and found the RIGHT hose out of the 347 hoses on the motor,set the `lead' about 8 she'd have linear power,i had 3 of those cads,great work cars! 100MPH cruise was nothing,i still have a 425 in an old suburban with the same `trick',at lowR's you lose vacuum and the dist esentially retards from where it was/what you've compensated for by`tuning' to be able to drive it( i don't know if i'm making sense on this?)

i have a `66 tri-power on(off now) mine,there's several`ports' blocked of with chunks of hose/bolts,i'm going to tidy some of that up but there must be ONE of those that would be correct for a vacuum advance setup,,you'll get it/good luck:cheers


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