Editing Pontiac (automobile) (section)

===Carburetors===
Pontiac used Carter 1-barrel [[carburetor]]s for many years but, by the time of the second generation, the V8 engines had switched mostly to 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 halfway. This was accomplished two ways, mechanically for the [[manual transmission]] models, and via a vacuum switch on the automatics. This went through various permutations as it was only a factory-installed option from 1957 through 1966.

Pontiac also had a square-bore 4-barrel at the time, but this was rated at lower horsepower than the Tri-Power. This carburetor was later replaced by the [[Quadrajet]], a spread bore. The term "Spread-bore" signifies the difference in sizes between the primaries and secondaries, using smaller primaries paired with larger secondaries for increased airflow at wider throttle with fuel delivery changes akin to the two-plus-four benefit of Tri-Power but with a single carburetor. The Quadrajet was not the only thing that gave the top GTO 400 engine and the 428 H-O engines the same horsepower as the 389 and 421. The new engine had redesigned cylinder heads with different valve angles and larger ports that allowed for larger diameter intake and exhaust valves.

By the end of the muscle car era, the Quadrajet setup had become common on Pontiac engines. The Quadrajet design continued until 1990 for Oldsmobile V8 applications, with added computer controls to meet emissions and fuel economy standards.