[Dick Boneske]

I believe the following info will be helpful to those of you buy/restoring Tripowers for your Pontiacs. There is a lot of mis-information about these setups. My pet peeve is those that say how hard Tripowers are to "tune!" If the setup is installed and set up properly, "tuning" is not a mystery as some suggest.

There were two float bowl castings--#7011997 for '59-'64 and #7029683 for '64-'66. They are identical functionally, but have some cosmetic differences. All of the '59-'66 end carbs had the same venturi size--1 5/16". The first picture is of 997 float bowl--some had the casting numbers on the side and some on the bottom of the bowl. The second picture is of the latest 683 float bowl. The most obvious difference is the tapped hole in the 997 float bowl fast idle cam boss and none in the 683 bowls. This fast idle cam boss is not used in any way on the end carbs in a Tripower setup.

All the '59-'66 end carbs did have the same airhorns (tops), casting #7013206. The repro airhorns are nearly identical to the OEM except for the air cleaner web which is thinner than the OEM pieces, as you can see in the attached pictures. Some criticize the repro because the "GM" logo is upside down, but if you examine OEM tops, you'll see that many of them also have the logo upside down. The repros have no casting number on the bottom side like the OEM's do.

There were several different versions of throttle body castings, mostly #15211, which appears only on the bottom of the throttle body. A few late '66 were casting #31344. The pictures attached show the minor differences. The early bases ('59-'63) had throttle stops that only allowed the throttle plates to open about 80%. All the '64-'66 end carbs had bases that allowed 100% throttle opening. It's not difficult to modify the earlier bases to allow full throttle opening by grinding off the cast iron stop until you can achieve 100% WOT.

The end carb throttle plates used on pre-'64 setups had no holes in them. For '64 and later, there was a .031" hole in the rear half of the throttle plate. I believe the holes are there to allow enough air to flow to create some fuel flow out of the float bowl to prevent the constantly evaporating gas from forming varnish deposits in the carbs. I have been drilling these holes in the Tripower setups I restore. I also apply the coating DAG213 to the top edges of the end carb throttle plates as the factory did to ensure a better seal from air leakage. Sometimes, the DAG213 is redundant if the throttle plates fit in their bores with no light showing around the edges. That is not usually the case, no matter how carefully you try to center them in the bore.

These carbs are very simple compared to other makes/models of carburetor. If you pay attention when disassembling them and carefully clean them, reassembly is not difficult. There are always people on this board to help you if you have questions during your rebuild or troubleshooting.

[Kenth]

The tapped hole in the 997 float bowls were used for the secondary lock mechanism controlled by the choke.

[Dick Boneske]

Originally Posted by Kenth

The tapped hole in the 997 float bowls were used for the secondary lock mechanism controlled by the choke.

Pontiac never used a mechanical choke lockout on '59-'66 Tripowers. The first picture shows the vacuum switch on the front of this '62 Pontiac Tripower setup.

Pontiac did use mechanical lockout on '57 & '58 Tripowers, as you can see in the last picture attached.

Pontiac used the coolant temperature-contolled vacuum switch to block vacuum to the secondary carbs. Vacuum was not available until the coolant reached about 120 degrees F.

I believe Cadillac used a mechanical lockout for the secondary carbs in '59, '60 thereabouts.

[Kenth]

Originally Posted by Dick Boneske

Pontiac never used a mechanical choke lockout on '59-'66 Tripowers. The first picture shows the vacuum switch on the front of this '62 Pontiac Tripower setup.

Pontiac did use mechanical lockout on '57 & '58 Tripowers, as you can see in the last picture attached.

Pontiac used the coolant temperature-contolled vacuum switch to block vacuum to the secondary carbs. Vacuum was not available until the coolant reached about 120 degrees F.

I believe Cadillac used a mechanical lockout for the secondary carbs in '59, '60 thereabouts.

You are correct.
I have found Cadillac also used the 997 secondary float bowl, thus the tapped hole for these.
FWIW

[Tom Vaught]

Thanks for the GREAT INFO Guys!

Tom V.

[Dick Boneske]

I thought I'd seen that mechanical lockout in a Cadillac Service Manual. Thank you for the feedback.