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Pontiac is a marque of automobile produced by General Motors and sold in the United States, Canada and Mexico from 1926 to the present. In the GM brand lineup, Pontiac is a mid-level brand featuring a sportier, high-performance driving experience for a reasonable price, and its advertisements appeal to younger customers. 
PMD originally used Carter 1-barrel carburetors for many years, but by the time of the second generation V-8 engines had switched mostly to the 2-barrel offerings. These also were the basis for the Tri-Power setups on the engines. The Tri-Power setup included one center carburetor with idle control and two end carburetors that did not contribute until the throttle was opened more than half way. This was accomplished two ways, mechanically for the manual transmission models, and via a vacuum-switch on the automatics. This went through various permutations before being banned by GM. PMD also had a square-bore 4-barrel at the time, but this was rated at a lower power than the Tri-Power. This carburetor was later replaced by the Quadrajet, a spread bore. 'Spread-bore' refers to the difference in sizes between the primaries and secondaries. By the end of the muscle car era, the QuadraJet setup had become the nearly-ubiquitous choice on PMD engines, due to its excellent economy and power characteristics. While QuadraJets have been occasionally derided as being poor performers, with proper understanding and tuning it can compete at most levels with other designs. This design proved good enough to last well into the 1980s with emissions modifications while most others carburetors were dropped for the easier to build fuel injection when economy mattered. 
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