Rochester's Quadrajet carburettors were a staple of General Motors V-8 powered vehicles from the late 1960s until the switch to electronic fuel injection was finished in the late 1980s. Capable of both fuel economy (for a V-8) and performance they made a name for themselves, although it is sometimes used as a curse.
When introduced it was the most complicated carburettor of its time, incorporating four-barrels and many functions (ie fast idle, choke). It was a fearsome rebuilding task for most technicians who were used to tuning Holleys and Carters. The myriad of linkages, internal circuits, and easily lost tiny pieces were incomprehensible to some. With age the Quadrajet earned a following of technicans who understood its design and recognized its potential.
The primary barrels of the carburettor are tiny compared to most four-barrel designs, but this is what gives the Quadrajet its gas milage edge. In contrast, the secondary barrels are huge, providing a performance edge. During normal driving the primary barrels are adequate for cruising speeds. The beast comes out when the pedal is depressed further. The secondaries open and there is the slightest amount of delay as the accelerator pump richens the mixture. A Quadrajet carburettor car is often distinguishable from other cars by the sound of the engine as the secondaries open. There is a moment of quiet followed by a large increase in exhaust volume, sometimes described as a 'booming' noise.
Most performance enthusiasts shun the Quadrajet as a stock carburettor laden with useless emissions controls. In reality, the Quadrajet offers performance on a par with most aftermarket carburettors while retaining good driveability and gas mileage. With a little modification most Quadrajets can easily reach 750cfm (cubic feet per minute) airflow.
There were many iterations of the Quadrajet, even including some electronic versions produced while General Motors were dragging their feet in changing to electronic fuel injection. The most desirable are the ones produced in the mid-seventies on big-block powered high-performance and luxury cars. These can flow up to 800cfm in the stock configuration.