Servicing The Rochester Quadrajet Carburetor

Accelerator pump arm fits as shown. This application uses the inner hole for a shorter stroke. Note the linkage position. The spring roll pin fits securely, centered to provide support for the arm. Make sure the arm's pivot hole is not worn badly. Fortunately, these arms can be matched readily if a replacement is necessary.

Polish needle ends of idle mixture screws. Install springs and turn screws to the bottoming point-gently. Do not seat the screw tightly. Back each screw out the number of turns listed in the factory specifications. Adjust these screws after engine warm-up, following service and tuning guidelines. Later applications have limiter caps or sealed screws.

Install a new vacuum break hose-avoid kinks. Earlier Quadrajet models are prone to inlet thread failure. Damaged fuel inlet threads should be restored properly with a Heli-Coil thread insert. (Don't waste time with other methods.) A pleated paper filter fits behind the fuel inlet nut. Install gasket and nut. Tighten nut to 25 ft-lbs.

Vacuum break link clearance is one of the critical measurements. In the instruction sheet, you will find references to each important adjustment. Follow details when adjusting linkage rod lengths and the secondary lockout. The choke and secondaries will not function properly unless these adjustments are correct.

The choke opens slightly as the vacuum break applies. This is an important measurement, listed on the specification sheet. As the engine fires, vacuum applies at the diaphragm, pulling the arm and choke lever. Use a quality gauge to measure the adjustments. Follow the adjusting sequences carefully.

Secondary linkage adjustments are crucial to Quadrajet performance. These adjustments determine whether the engine will respond properly under partial and full-throttle acceleration. For the 4MV models, there are "3-point pickup" and "2-point pickup" linkage systems noted in factory workshop manuals. Identify your carburetor's type.

The choke opens slightly as the vacuum break applies. This is an important measurement, listed on the specification sheet. As the engine fires, vacuum applies at the diaphragm, pulling the arm and choke lever. Use a quality gauge to measure the adjustments. Follow the adjusting sequences carefully.

Secondary air valve's spring tension is precisely calibrated. If the tension needs adjusting or you suspect that it is incorrect, follow adjustment steps in your Corvette factory workshop manual. Match a new base gasket to carburetor and manifold. Torque the carburetor mounting bolts and nuts to 14 ft-lbs. Do not over-tighten. Recheck the mounting hardware torque after engine warm-up. Job done!