Tri Power & Max Displacement - Pontiac GTO Forum
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post #1 of 5 (permalink) Old 12-17-2018, 09:01 AM Thread Starter
 
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Tri Power & Max Displacement

I am considering building a larger (455 cubic inch +), more powerful motor, but want to keep the tri power. Does anyone have reference material to the maximum flow through the tri power setup and at what HP levels it would be the bottle neck ? (Sorry I have searched and not found anything.)

1965 GTO Convertible 3 speed tri-power drum brakes originally

Current setup:
400 cu in with tri-power
4 speed Muncie
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post #2 of 5 (permalink) Old 12-17-2018, 11:48 AM
 
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I have not personally had any experience with a tri-power. But, there have been plenty of 11 sec drag cars running a tri-power. Norman Warling has even run high 11's with his tri-power 389 '62 Cat Stocker.

There are a few guys who specialize in tri-power stuff. They can probably answer all your questions.

http://www.pontiactripower.com/

"...A strong 461 Pontiac motor was built and run with a 750 cfm Holley and compared to a 66 tripower. The Holley induction motor made 493 HP and peak of 552 ft lbs. torque. The tripower induction unit on the same motor put out 477 HP and 545 ft lbs torque. ..."

If you can't make all the power you want with Roch carbs, I think you can adapt Holley 2-barrels. Won't look stock. But you'll have three 2-barrels & more power. Guessing that much cheaper adapters are available.

https://www.ebay.com/i/233037733365?chn=ps

https://www.speedwaymotors.com/Holle...saAmHpEALw_wcB
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Last edited by bigD; 12-17-2018 at 12:47 PM.
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post #3 of 5 (permalink) Old 12-17-2018, 07:29 PM
 
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Originally Posted by cij911 View Post
I am considering building a larger (455 cubic inch +), more powerful motor, but want to keep the tri power. Does anyone have reference material to the maximum flow through the tri power setup and at what HP levels it would be the bottle neck ? (Sorry I have searched and not found anything.)
The larger outer carbs flow about 250 CFM's from everything I have read. Not sure what the smaller center carb on a '65 Tri-Power flows. I would use the '66 intake having the larger carb. So that means you are getting 750 CFM's. Q-jet is 750 CFM's.

Just for reference, the 3-Holley carb set-up flows a total of about 930 CFM's even though they are 2 500CFM and 1 350 CFM carb totaling 1350 CFM's. Holley rates their 2 Bbl carbs differently then their 4 Bbl carbs, so all three give you about 930 CFM's. The outboard carbs, if stock as found on the Six Pack, are vacuum operated and do not have the mechanical linkage like the Pontiac tri-power.

I would use the tri-power and see how it does. If you are handy with tools, I would gasket match the intake runners and polish them up a little. Probably will have to play around with the jetting to get it dialed in. I would also put spacers under the carb, maybe the phenolic 1/2" if you don't already have them. I see K&N now offers what they claim is an improved air filter for the tri-power. I might try them as you want good air flow.

So I think I would try them unless you plan on going with some big lift roller cam, high RPM's, or huge flowing heads.
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post #4 of 5 (permalink) Old 12-17-2018, 11:33 PM Thread Starter
 
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Thanks Gents! From some additional reading on the www, it appears the Rochester tri power flows upwards of 900 cfm. I keep thinking a nicely built 455 or 461 would be nice . Thanks for the help!

Chris

1965 GTO Convertible 3 speed tri-power drum brakes originally

Current setup:
400 cu in with tri-power
4 speed Muncie
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post #5 of 5 (permalink) Old 12-21-2018, 07:55 PM
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I'll add, if it's a street engine, no worries. If you are looking at 550HP or more, you'll need to run a different intake and carb(s). In a road test done back in the day, a magazine ran a 428 powered '68 GTO with the stock Quadrajet, and then swapped to a stock '66 Tripower. They ran the quarter mile 3 or 4 times with each set up. With no other changes at all, the tripower made the car a full half second faster on every pass. I myself have run the stock tripower on my '65 GTO for the past 37 years. Very reliable and very good performance. I ran a stock '66 tripower on my stock '67 GTO 400 years ago, and the difference between it and the quadrajet was quite noticeable....the car pulled much harder with the trips, and my butt dyno told me it probably was making 40-50 more HP. I would have no issue running a '66 tripower on a 455-461 street engine.
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