Metering Rod & Jet Specs Carter AFB
Accelerator pump circuit (AFB)
The AFB (Aluminum Four Barrel) carburetor was produced by Carter for original equipment cars from 1957-1971. The AFB was then available as a high performance 9000 series carburetor up until the late 1990's. Weber is currently making the AFB now known as the Edelbrock. The accelerator pump controls response when pressing down on the gas pedal. Too little squirt will cause a flat spot or hesitation, too much squirt can cause black smoke and/or sluggish acceleration. You can change the action of the accelerator pump by re positioning the accelerator pump linkage. The metering rods are of a step design and are controlled by vacuum and metering rod spring action. At low speeds the **metering rod** is dropped down into the primary main jets, thus partially closing off the flow of fuel. At higher speeds and less vacuum the rods pull up from the main jets allowing more fuel to flow. AFBs use mechanical secondary's. Punch the gas pedal and the secondary's will open.The early AFBs were not rated with CFM statistics, but the later performance 9000's were.
Look for 4 numbers followed by a S. Example 3445S. You may find other numbers stamped on the carburetor, but they are usually the part numbers of the part they are stamped on. An example would be 0-1654S. We have carburetor kits for most Carter AFB Carburetors including the 4000 compitition series and the 9000 compitition series.
Flooding, stumble on acceleration, and other performance complaints are, in many instances, caused by the presence of dirt, water, or other foreign matter in the carburetor. To aid in diagnosing the cause of the complaint, the carburetor should be carefully removed from the engine without draining the fuel from the bowl. The contents of the fuel bowl may then be examined for contamination as the carburetor is disassembled.
Check the fuel in the bowl for contamination by dirt, water, gum, or other foreign matter. A magnet moved through the fuel in the bowl will pick up and identify any iron oxide dust that may have caused intake needle and seat leakage.
Inspect gasketed surfaces between body and air horn. Small nicks or burrs should be smoothed down to eliminate air or fuel leakage. Be especially particular when inspecting the top surface of the inner wall of the bowl around the vacuum piston passage. A poor seal at this location may contribute to a “cutting-out” on turns complaint.
Fill the carburetor bowl with clean fuel before installing on the manifold. This will help prevent dirt trapped in the fuel system from being dislodged by the free flow of fuel as the carburetor is primed. The operation of the floats and intake needle and seats may be checked under pressure if a fuel pump is used at the bench to fill the carburetor bowl. Operate the throttle several times and visually check the discharge from the pump jets. We have instructions on bench testing the bowl on the Accelerator Pump Circuit page.
Before installing the carburetor, hold choke valve open and turn the idle speed screw until it just contacts the throtle lever, then 1/2 a turn more to open the throttle valves enough to keep the engine running until the idle mixture and final RPM adjustment can be made.