PontiacJim
Member
The tri-power, Six Pack, trips, 3 deuces, or whatever else you want to call them have been around for a long time. Never understood the comments on "they are hard to tune/synchronize."
I suppose it may have stemmed from the foreign cars and their SU carbs, early intakes using the Stromberg carbs, those guys who threw 3 carbs all having idle circuits, or even a false assumption by the motorcycle guys who had to sync their multiple carbs. The set-up is pretty straight forward with regards to the GM products using the Rochester carbs. Olds had the J-2 option, Pontiac had the Tri-Power, Chevy had them, and even Caddy had a 3 x 2 set-up - I've owned them all to include an Olds engine with the Offenhauser intake and 3 x 2 Stromberg 48's.
The early Pontiac's used a vacuum operated system for the outboard 2 carbs. Not the best set-up in my opinion. Problems could develop if they stuck open and they were sluggish compared to the later designed mechanical linkage. Outboard 3 x 2 Rochester carbs did not have the idle circuit, they have different bases as opposed to the center carb. So they are simply sitting there dead until opened up. The outboard carbs used a linkage rod with clips, not nuts or rods to adjust. I have seen adjustable linkages, but most were aftermarket applications. Never had a problem with "out of adjustment" with them.
Installed the 340 Six Pack set-up on my brother's 360 build. I am not a fan of Holley carbs, period. The set-up is a complete factory reproduction with the aluminum Edelbrock dual-plane intake, 2-Bbl Holleys, linkages, and vacuum opened outboard carbs(no idle circuits), and air cleaner. Works perfect and he has had no problems with them after several years of running it. The key is to understand how the system works before trying to make adjustments. I did not have to make any adjustments on the Six Pack as it ran fine out of the box. I am sure most just jump in and "tinker" with stuff not knowing what they are doing and then get the system out of whack, call it junk, and pull the unit to replace it with a single 4-Bbl because they listened to those who said the single 4-bbl is so much simpler and runs better - suppose that is true if you don't know what you are doing.
The Six Pack's Holley 2-Bbl carbs are advertised at 350 cfm for the center and 500 cfm for the outers, but two-barrels are rated at a different pressure drop from four-barrels, so the cfm number is inflated. In four-barrel terms, these carbs collectively flow about 975 cfm. It is important to note that this is a dual-plane intake. From what I have seen on Ebay, the Offenshauser 3 x 2 intake is a single plane intake and looks to be of a low profile design. I have seen pics for both the 3-bolt base carb pattern (stombergs) and the 4-bolt base pattern and they were available for the B & RB engines. The single plane manifold is not the best for a street car and present problems unto itself. So if me, I'd stick with the factory set-up known to work or at least know what you are getting into when looking to add an aftermarket tripower set-up. Yep, they do look cool, but so do dual quads, tunnel rams, cross rams..........
I suppose it may have stemmed from the foreign cars and their SU carbs, early intakes using the Stromberg carbs, those guys who threw 3 carbs all having idle circuits, or even a false assumption by the motorcycle guys who had to sync their multiple carbs. The set-up is pretty straight forward with regards to the GM products using the Rochester carbs. Olds had the J-2 option, Pontiac had the Tri-Power, Chevy had them, and even Caddy had a 3 x 2 set-up - I've owned them all to include an Olds engine with the Offenhauser intake and 3 x 2 Stromberg 48's.
The early Pontiac's used a vacuum operated system for the outboard 2 carbs. Not the best set-up in my opinion. Problems could develop if they stuck open and they were sluggish compared to the later designed mechanical linkage. Outboard 3 x 2 Rochester carbs did not have the idle circuit, they have different bases as opposed to the center carb. So they are simply sitting there dead until opened up. The outboard carbs used a linkage rod with clips, not nuts or rods to adjust. I have seen adjustable linkages, but most were aftermarket applications. Never had a problem with "out of adjustment" with them.
Installed the 340 Six Pack set-up on my brother's 360 build. I am not a fan of Holley carbs, period. The set-up is a complete factory reproduction with the aluminum Edelbrock dual-plane intake, 2-Bbl Holleys, linkages, and vacuum opened outboard carbs(no idle circuits), and air cleaner. Works perfect and he has had no problems with them after several years of running it. The key is to understand how the system works before trying to make adjustments. I did not have to make any adjustments on the Six Pack as it ran fine out of the box. I am sure most just jump in and "tinker" with stuff not knowing what they are doing and then get the system out of whack, call it junk, and pull the unit to replace it with a single 4-Bbl because they listened to those who said the single 4-bbl is so much simpler and runs better - suppose that is true if you don't know what you are doing.
The Six Pack's Holley 2-Bbl carbs are advertised at 350 cfm for the center and 500 cfm for the outers, but two-barrels are rated at a different pressure drop from four-barrels, so the cfm number is inflated. In four-barrel terms, these carbs collectively flow about 975 cfm. It is important to note that this is a dual-plane intake. From what I have seen on Ebay, the Offenshauser 3 x 2 intake is a single plane intake and looks to be of a low profile design. I have seen pics for both the 3-bolt base carb pattern (stombergs) and the 4-bolt base pattern and they were available for the B & RB engines. The single plane manifold is not the best for a street car and present problems unto itself. So if me, I'd stick with the factory set-up known to work or at least know what you are getting into when looking to add an aftermarket tripower set-up. Yep, they do look cool, but so do dual quads, tunnel rams, cross rams..........
