Triopower Small Center Carb
 

There you have it--97 pieces are used in the center carb used for Pontiac Tripowers from '57-'65. The automatic version had five more pieces for the hot idle vent. When restoring these carbs, every one of those pieces needs cleaning/plating/dichromating, or replacement. The jetting and venturi cluster idle circuits were unique to each engine---cubic inches, cam, transmission, etc.

The '57-'65 center Tripower carb saw only minor changes for the nine years Pontiac used that carb for Tripowers. From '61-'65, the venturi opening was enlarged to 1 1/4". Some of you are aware that the "larger" center carb used in '66 actually had a venturi opening measuring 1 3/16"-- smaller than the "small" center carb. The '66 obviously had larger throttle plates, but the venturi was smaller. I think Rochester did that to improve throttle response with the '66 setup.

Pretty cool!

Do you think a stock '65 tri-power set up can make 500hp on a 455 without major modifications? Or, too restrictive?

I know the Glory Days '65 GTO ran mid 10's in the 1980' with a '66 Tripower. That takes more than 500 HP. The engine was built by the late Dan Whitmore of Gennesee, Wisconsin.

The cast iron manifold was ported to the max, the heads were '70 RAIV, engine 462. The carbs had all the air cleaner webs removed and the center carb choke removed. The heat riser passage was cut from the cast iron manifold (huge project).

I believe 500 HP with Tripower is very doable now with aluminum heads RA heads, either Edlebrock or Kaufmann. I have modified end carbs to 1 7/16" venturi openings. The center carb can also be opened to about 1 3/8" from the stock 1 1/4".

Everyone says the flow restriction is with the manifold. Hard to figure when you compare the Tripower intakes from '64, '65, and '66 with the aluminum RAIV intake. The runners are similar, but modified Tripower carbs surely flow more than a Quadrajet. I'm not knocking Quadrajets, but they are 850 cfm max. A modified set of Tripower carbs on a ported intake can do better. JMHO. I wish someone would pursue this.

My 1965 421 Tripower bored and stroked to 454 with ported 670 iron heads produced 492 HP.
Tripower restored by Mike Wasson and motor done by Butler Performance.

We made close to 600hp with the stock '65 carbs, intake was port matched to RA4 size. This we with e-heads. Made 550ish with same setup but with 197HO heads

Dick,
Is the hot idle vent you refer to the flapper that closes when the carburetor is off idle.? So is it not necessary on manual transmission cars? Is that the same thing that is referred to as a "hot idle compensator"?

Thanks for your info, Les

No. It is a thermostatic valve on the rear of the center carb that opens when the engine is hot to supply additional air at idle. Manual transmission cars did not have this feature.

So what is the little valve on the top of the center carb, that is operated by the rod that connects the throttle? I have an old parts carburetor that does not have that. Should it be on my 62 with manual?

All 1959-66 Tripower center carbs, and most 1958-67 2GC, uses the idle vent valve.