Early engines were adequately supplied with a fuel/air mixture by simple one-barrel carburetors. As displacement increased and cylinders were added the addition of a second barrel to the carburetor met the increased demand. At idle and lower RPM operation a one two-barrel carburetor supplied sufficient fuel/air input for everyday driving operations. However, extra fuel/air was needed when the engine was operating at higher RPM in applications such as racing.
To satisfy this need multi-carb setups were created to supply additional fuel/air in the days when 4-barrel carburetors were not yet available. When the 4-barrel carburetors were introduced they all but eliminated the multi 2-barrel setups because the 4-barrel eliminated the problems of synchronizing linkage by incorporating everything into one package. Multi carb 2-barrel setups still were used in many performance applications for many years though. Especially in racing and hot rod applications.
Now we only see these multi-carb setups on hot rods and nostalgia themed vehicles. This is especially true on what are commonly referred to as alternate engines. Those other than the smallblock Chevy V8 or the new crate motors. Buick Nailheads, Cadillacs, Oldsmobiles, Chrysler Hemis and Y-block Fords are the most popular of these engines.
Most of these multi-carb setups shared a number of things in common. They had one carburetor that was the main carb equipped with a choke and actuated by the throttle linkage. The additional carburetors were tied together by linkage and were actuated by an adjustable link from the main carburetor linkage. The additional carburetors had no choke and only came online when additional demand for fuel/air was indicated.
To illustrate how one of these setups works we have included the following photos that show a Buick Nailhead tri-carb manifold equipped with three Rochester 2-jets. The manifold, carburetor conversion kit and linkage kit are all from Eelco, PO Box 1127, Canby, OR 97013. Additional information about this kit and other kits they have for popular engines is available on their web site www.eelcoequipped.com.