Quadrajet
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:Fortunately, leaking well plugs is primarily a problem only on the first few years of production when pressed in cup plugs were used instead of the later (and better) spun-in aluminum plugs that were swaged in place. Many Quadrajets have their fuel bowl plugs sealed with epoxy when rebuilt to prevent leaks. This may be good for a short time but epoxy will not stand up to the extreme conditions (heat and fuel contact) encountered for long. | :Fortunately, leaking well plugs is primarily a problem only on the first few years of production when pressed in cup plugs were used instead of the later (and better) spun-in aluminum plugs that were swaged in place. Many Quadrajets have their fuel bowl plugs sealed with epoxy when rebuilt to prevent leaks. This may be good for a short time but epoxy will not stand up to the extreme conditions (heat and fuel contact) encountered for long. | ||
* The small float bowl 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 worn fuel pump, pump push rod, or camshaft eccentric. In normal driving and even off road performance use it provides excellent control of the fuel level. | * The small float bowl 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 worn fuel pump, pump push rod, or camshaft eccentric. In normal driving and even off road performance use it provides excellent control of the fuel level. | ||
| − | * The fuel inlet/fuel filter housing threads tend to be very fragile. It is common for the fuel inlet threads in the main casting to strip. There are several "fixes" available in the aftermarket: New oversize self-tapping fuel filter housings; new fuel filter housings that seal with O-rings; and Heli-Coil rethreading kits. | + | * The fuel inlet/fuel filter housing threads tend to be very fragile, especially when exposed to ethanol since the mid-2000s. It is common for the fuel inlet threads in the main casting to strip. There are several "fixes" available in the aftermarket: New oversize self-tapping fuel filter housings; new fuel filter housings that seal with O-rings; and Heli-Coil rethreading kits. |
| − | * Almost all Quadrajets today have some amount of warpage of the castings. The root cause of this warpage is often over-tightening the front two carburetor mounting bolts, often in combination with a base gasket that doesn't have hard nylon inserts for the bolt holes. Without the inserts the base gasket can compress, warping the castings. | + | * Almost all Quadrajets today have some amount of warpage of the castings. The root cause of this warpage is often over-tightening the front two carburetor mounting bolts, often in combination with a base gasket that doesn't have hard nylon inserts for the bolt holes. Without the inserts the base gasket can compress, warping the castings. A warped casting and/or airhorn can be unwarped using a special tool or sent to a professional service. |
* The steel primary throttle shaft will tend to wear the aluminum casting material. This results in an air leak and in extreme cases could cause the primary throttle blades to not close properly. This can result in poor idle quality and unfiltered air to be pulled into the engine. The aftermarket has responded; several vendors are supplying bushing repair kits for the Q-jet throttle body. | * The steel primary throttle shaft will tend to wear the aluminum casting material. This results in an air leak and in extreme cases could cause the primary throttle blades to not close properly. This can result in poor idle quality and unfiltered air to be pulled into the engine. The aftermarket has responded; several vendors are supplying bushing repair kits for the Q-jet throttle body. | ||
| + | * The idle tubes (which are located in the main casting) are usually sized at .031" or smaller (especially if it was used with a Chevrolet 305 in truck/van or passenger cars (including the E4M and dual discharge pump models) which is retained with a slip collar. This is usually overlooked where the bottom of the idle tubes are usually plugged up with debris - hence the 'Quadrajunk' slang. Idle tubes can be fine-tuned and opened up with numbered drill bits. | ||
==Q-jet variants== | ==Q-jet variants== | ||
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