Tri-Power Carburetor

Whether you call it a Tri-Power, a six pack, or triple two-barrels, multiple carburetion is considered a high performance package. Even if they do run poorly, the “eye candy” appeal under the hood is unmistakable. Like most multiple carburetion, the Rochester 2G carburetors in this application do not work very well. In an effort to keep tuning simple for service technicians, only the center carburetor was made with an idle circuit. A person only needs to adjust the two idle mixture screws, just like any other two or four-barrel single carburetor.

The problem with this is that the two outboards still leaked air around the four throttle plates, and no matter how precisely aligned they were, a lean air/fuel mixture was delivered to the front and rear cylinders. This resulted in a rough idle. With precision plate alignment and some internal engineering improvements, this issue can be minimized, but the engines will never idle perfectly - it just won’t happen.

A second problem exists with the Tri-Power set up. On all but a few Pontiac and Olds manual transmission applications, the outboard carburetors are opened by a large diaphragm. The driver has no direct control of the opening. Venturi vacuum is supplied to this diaphragm through a vacuum slider switch. The system works on the speed of the air going through the center carburetor. By producing venturi vacuum, and at higher throttle positions, the two outboard carburetors open. The problem is not with the system, but with the drivers and mechanics who simply do not understand the system’s workings. They typically remove the vacuum diaphragm and the slider switch and then fabricate various “manual” linkage apparatuses to open the outboards. Not professional engineering by any stretch, and you can only imagine the complications arising here!

At the shows however, hood open, nothing draws more comments than a Tri-Power!

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