page_title: Quadrajet
section_title: Drawbacks
hierarchical_section_title: Quadrajet / Drawbacks
caption_attribution_description: English: 1982 Rochester Quadrajet carb. It is an M4ME model, which is the later casting, and has an electric choke. This is my carb taken with my camera, so there are no fair use issues here.
context_page_description: The Quadrajet is a four barrel carburetor, made by the Rochester Products Division of General Motors. Its first application was the new-for-1965 Chevy 396ci engine. Its last application was on the 1990 Oldsmobile 307
  V8 engine, which was last used in the Cadillac Brougham and full size station wagons made by Chevrolet, Pontiac, Oldsmobile, and Buick.
context_section_description: Significant negative features of the Quadrajet were:
  Its leaky fuel bowl. As in nearly all carburetors, the Quadrajet's bowl had pressed-in plugs used to seal holes left after drilling fuel passages during the manufacturing of the carburetor. These plugs in the Q-jet sometimes leaked fuel causing difficult cold-engine starting, erratic idling, poor fuel mileage, and excessive emissions. Many Quadrajets have their fuel bowl plugs sealed with epoxy when rebuilt to prevent leaks.
  The very small float bowl/fuel chamber can result in fuel starvation in extreme high-performance situations, but can usually be traced to a fuel delivery problem to the carburetor, such as a weak fuel pump or a worn/rounded camshaft eccentric that drives the fuel pump lever. The latter situation can be resolved with an external (electric) fuel pump.
  The fuel inlet/fuel filter housing threads tend to be very fragile. When care is not taken to align the insert, it is possible for the fuel inlet to cross-thread and to strip when tightened in the main housing. There are several "fixes" available in the aftermarket:  New, oversized, self-tapping fuel filter inserts; new fuel filter inserts that seal with O-rings; and Heli-Coil re-threading kits. In nearly all cases, the carburetor will require dis-assembly and internal cleaning of the aluminum thread residue, especially up to and including the needle and seat, (needle valve), to prevent flooding.
  Almost all Quadrajets today have some amount of warpage of the castings although less pronounced in the so-called "mod Quad" versions after 1974 which were a bit heavier and better designed to resist warping. The root cause of this warpage is over-tightening the front two carburetor mounting bolts, often in combination with a base gasket that lacks hard nylon inserts for the bolt holes.
  Over much use, the steel primary throttle shaft will tend to wear the aluminum casting material in the throttle body. This results in a minor air leak and in extreme cases, can cause the primary throttle blades to not close properly. This results in poor idle quality. The carburetor parts vendor QuadrajetParts.com offers repair kits for the carburetor body that allow easy repair by installing bronze bushings.
  The carburetors have been billed as difficult to tune and unreliable by some, however, many times this is simply attributed to the lack of knowledge of the unit itself. Consequently, many Quadrajets were replaced with other brands of carburetors in an often ill-fated attempt to rectify a problem that was not caused by the carburetor. When properly tuned, the Quadrajet is both an efficient and effective performing carburetor.
caption: A Quadrajet M4ME carburetor with electric choke. The Quadrajet went through several changes in its lifetime.
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