GM Corvette 1963-1982 Repair Guide

Carter WCFB Carburetor


See Figures 1, 2 and 3

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Fig. Fig. 1: Carter WCFB upper bowl cover parts

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Fig. Fig. 2: Carter WCFB lower bowl cover parts

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Fig. Fig. 3: Carter WCFB throttle body parts

The Carter WCFB is the standard carburetor on 1963-65 Corvettes.

Functionally, it is two dual carburetors mounted in a single housing and is comprised of four basic components: choke housing, top cover, main body, and throttle flange. The metering rods, accelerator pump, and choke are located in the primary side of the carburetor body. It has the five conventional systems: float, low speed, high speed, accelerator pump, and choke.


Idle Speed and Mixture

Idle speed and mixture adjustments are best accomplished using a tachometer and vacuum gauge. Make this adjustment with the air cleaner installed.

Bring the engine to operating temperature, check to see that the choke is fully off, and adjust the idle-speed adjustment screw to give 475 rpm (450 on automatic transmissions in Drive range). Adjust the idle-mixture adjustment screws separately until peak vacuum and rpm are indicated on the vacuum gauge and tachometer.

An alternative method is to set the idle-mixture screws lean to a beginning, rough idle, then back screws out (enrichen) 1 / 4 turn. Never bottom the idle-mixture adjustment screws or possible damage to the needle seat may result.

Automatic Choke

The choke is correctly set when the index mark on the plastic cover aligns with the corresponding mark on the choke housing. The introduction of dirt, gum, water or carbon into the choke housing or vacuum passage can detrimentally affect engine performance. Check this system periodically and clean if necessary.

Intermediate Choke Rod

The intermediate choke rod adjustment requires the removal of the choke coil housing assembly, gasket, and baffle plate. Open the choke valve and position a 0.026 in. wire gauge between the bottom of the slot in the piston and the top of the slot in the choke piston housing. Seat the choke piston on the gauge. The measurement between the top of the choke valve and the air horn divider should be 0.096 in. Adjustment is made by bending the intermediate choke rod.


To make the float adjustment, remove the top cover then disassemble and reassemble the floats without the cover gasket. Make the lateral adjustment by placing the 1 / 4 in. float gauge (supplied in the carburetor overhaul kit) under the center of the secondary float so that the notched portion of the gauge fits over the edge of the casting. Bend the floats until their sides just clear the vertical uprights of the gauge. Repeat the adjustment on the primary float using either the 1 / 8 in. float gauge or a 1 / 8 in. drill bit.

The vertical adjustment is correct when the floats just clear the horizontal bar of the gauges when the gauges are positioned as described above. The required clearance between the top of the floats and the bowl cover is 1 / 8 in. on the primary floats and 1 / 4 in. on the secondary floats.

Float drop measurement must be made with the top cover gasket removed. Measure between the lowest point of the floats and the bottom of the top cover. This should be 2 in. for both primary and secondary floats. Adjust the accelerator pump by backing off the idle-speed adjustment screw and positioning the float-drop adjustment gauge (supplied in rebuilding kits) on the dust cover boot. Bend the top flat of the pump arm so that it is parallel to the gauge.

Metering Rod

To adjust the metering rods, back off the idle-speed adjusting screw until the throttle valves are fully seated, then loosen the screw in the metering arm. Depress the metering rod arm upward until it just touches the hanger. Secure the arm with the set screw.

Unloader and Secondary Throttle Lever

Make the unloader adjustment with the throttle valves wide open. Measure between the inboard edge of the choke valve and the center wall of the top cover. Bend the unloader tang to obtain a 3 / 16 in. clearance.

Turn the carburetor upside down to adjust the secondary throttle lever. With the primary valves wide open, the secondary valves should be within 4° to 7° of the wide open position. Bend the connector rod at its upper angle until actuation of the throttle linkage fully opens the primary valves. Bend the tang on the secondary throttle dog so that with the primary throttle valves open, the secondary throttle-to-bore angle will be 5 1 / 2 °. There should be 0.017 in.-0.022 in. clearance between the positive closing shoes on the primary and secondary throttle levers with the throttle valves closed.


  1. Remove the carburetor from the engine, but do not drain the fuel in the bowl. Tap the filter nut lightly with a hammer, then remove the inlet nut and gasket and lift out the filter.
  3. Disconnect the choke connector rod, intermediate choke rod, and throttle rod. Remove the metering-rod dust cover and vapor vent arm. Loosen the pump operating arm and metering-rod arm securing screws, and withdraw the countershaft.
  5. Remove the metering rod arm and link. Turn each metering rod 180° and lift them from the anger. Do not lose the two metering rod discs.
  7. Remove the top cover, lifting straight up so as to avoid damaging the floats, vacuum piston, or plunger assembly. Be sure the cover gasket is free of the bowl before lifting the cover. Mark the floats before removing them from the cover, to avoid unnecessary bending during assembly adjustments.
  9. Remove the secondary float needle, seat, and gasket, and group together. Remove the pump plunger assembly and spring and soak the leather pump plunger in gasoline or kerosene to prevent it from drying out. Turn the vacuum piston 1 / 4 turn to disconnect and remove the piston link.
  11. At this time, check the fuel in the bowl for contamination. Sweep the bottom of the bowl with a magnet while the fuel is still present. This will pick up iron oxide dust or metallic particles. Water contamination will appear as milky globules at the bottom of the bowl.
  13. Invert the carburetor body and remove the pump jet cluster and gasket. Tap out the pump discharge needle. Attach a 5 / 16 in. six-point socket to a six-inch extension and pry the pump inlet ball retainer and check ball from the bottom of the pump cylinder well.
  15. Remove the primary metering rod jets from the pump side of the carburetor. Remove the secondary main jets but do not mix them as their orifices are not the same size. Check the low speed jets to see that they are angled slightly on installation. The antipercolator plugs and bushings and main discharge nozzles are a press fit and should not be removed.
  17. Separate the throttle flange and carburetor body. Remove the idle-mixture screws and springs, throttle-lever adjusting screw, washer, and spring. Remove the fast-idle cam assembly and lockout arm. Remove the primary/secondary throttle valve connector rod. Back out the primary throttle shaft screw and washer and remove the throttle levers. Dislodge the secondary throttle return spring. Remove the primary and secondary-throttle valves and shafts. It will be necessary to file the staked ends of the throttle valve securing screws before they can be removed. Remove the choke housing and baffle.
  19. Clean and inspect the disassembled components. Use a carburetor cleaning solution to wash everything but the coil housing assembly and pump plunger. Clean the choke housing assembly in gasoline. Reassembly is the reverse of this procedure.