Rochester Quadrajet

Rochester Quadrajet
How It Began

The Quadrajet was released in 1965, and since then, saw a long and fruitful life installed on GM cars until EFI took over. The Quadrajet was actually the successor to the previously-built Rochester 4GC carburetor that was manufactured from 1952 to 1967. This new carburetor was blended with what Rochester knew about carburetors, mixed with ideas from other manufacturers, (spread-bore design and vacuum secondaries).

The Quadrajet became an instant success.
When part-throttle cruising, the small primaries (1 3/32-inch for 750 cfm, and 1 7/32-inch for 800 cfm carburetors) deliver a higher velocity into the intake than other carburetors. This results in better fuel atomization going into the intake. This, of course, is dependent upon whether the fuel metering, float level, idle-screw setting, throttle-blade angle, jets, power valve, air bleeds, and needle valves, etc., are all properly set.

While there are some GM street-car enthusiasts that swear by the Quadrajet, they are also disliked by almost as many. The stigma surrounding the Quadrajet has to do with the perceived lack of performance capabilities, and because rebuilding them is not quite as easy as, let’s say, a Holley. Many even call them Qaudrabog carburetors because of the “bog” that occurs when the secondaries open.

Since this actually occurs when the carburetor is not properly tuned, it is an ill-conceived, derogatory name. Either way, parts are easy to find, and a properly rebuilt Quadrajet will perform just as well as many aftermarket units when used in a proper application. In fact, even Chrysler used Quadrajet carburetors in the late ’80s, proving their popularity over the Carter Thermoquad with the engineers at Mopar.

Few people still fail to realize that the Quadrajet has a strong racing heritage within the Stock and Super Stock drag racing classes. In fact, there have been a multitude of record-holding Super Stock race cars that have run in the 9-second bracket with a Quadrajet on top of their manifolds.

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Rochester Quadrajet

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