The Rochester 2BBL carburetor was first used on the Chevrolet 265 cid V-8 in 1955. The 2BBL remained in production in various styles until the late 1970's. A popular application for the Rochester 2BBL was on the Pontiac tri-power GTO. Hard starting and hesitation may indicate that it is time to rebuild your Rochester 2BBL. Dirt, rust and water may have contaminated the insides of the carburetor, preventing it from operating correctly. Rebuilding a Rochester 2BBL can be done at home using commonly available tools.
Verify that you have the correct rebuild kit by comparing the number on the carburetor to application guide included with the kit. Disconnect the fuel line, choke wire and throttle linkage from the carburetor. Remove the carburetor from the vehicle and place it on a work bench.
Unscrew and remove the choke housing, air horn and venturi cluster. Remove the throttle body, float assembly, power piston and accelerator pump assembly. Carefully unscrew and remove the main metering jet from the bottom of the float bowl.
Soak all parts in carburetor dip until all dirt and gasket material has been softened. Do not place any plastic or rubber parts in the dip or they will be destroyed. Rinse off the parts in clean water and dry with compressed air. Clean all parts thoroughly including internal ports and passages until all traces of dirt and varnish are removed. Scrub the parts with an old tooth brush or pipe cleaners as required. Repeat this step as many times as necessary to ensure the carburetor parts are absolutely clean of all foreign material.
Reassemble the carburetor in the reverse order of assembly. Consult the rebuild kit's specification chart for the necessary adjustments and assembly guide.
Adjust the float drop before attaching the air horn to the carburetor body. Turn the carburetor upside down and measure the distance from the bottom of the float to the machined gasket surface of the float bowl. Bend the float tang until the measurement is correct according to the specification chart for your exact carburetor model number. Ensure this adjustment is correct before proceeding with the reassembly of the carburetor. The float level adjustment is critical to the final performance of the carburetor and cannot be changed once the carburetor is reassembled and installed on the vehicle.
Adjust the pump rod, idle vent, vacuum break, choke rod and vacuum switch according to the specification chart. These adjustments can be made with the carburetor installed on the vehicle, but it is much easier to do them with the carburetor still on the work bench.
Install the carburetor on the vehicle in the reverse order of removal. Start the engine and bring it up to normal operating temperature. Adjust the idle speed, the idle mixture screws and the fast idle speed. Ensure the throttle plates open completely and that they do not drag or bind.
