See Figure 1
- Remove the carburetor.
- Remove the air horn.
- Invert the main body and let the weight of the float rest on the needle and seat.
- Using a T-scale, check the distance between the gasket surface of the fuel bowl (gasket removed) and the top of the float at the center. The gap should be 7 / 32 ".
- If adjustment is necessary, hold the float against the bottom of the float bowl and bend the lip towards or away from the needle.
When bending, don't allow the float lip to push against the needle. The tip of the needle will compress and give a false reading.
- Recheck your adjustment a couple of times. It is [cf2]very important that the float lip be perpendicular to the needle +- 10° after the adjustment!
- Assemble the carburetor.
Fast Idle Cam
- Position the fast idle speed adjusting screw so that it contacts the second highest step of the cam. Move the choke valve toward the closed position with light pressure on the choke linkage.
- Insert a #44 drill bit between the upper edge of the choke plate and the wall of the air horn on all engines except the 8-318 with the Clean Air Package. On these engines, use a #20 drill bit. A slight drag should be felt.
- If adjustment is necessary, bend the fast idle link at the upper angle until the specified drill bit fits between the choke plate and the wall of the air horn.
- If the adjustment is to be made on the engine (with the engine running at curb idle), back off the fast idle screw until the choke can be closed to the kick position. Note the number of screw turns required so that the fast idle can be returned to the original adjustment.
- If the adjustment is to be made off the engine, open the throttle valve and move the choke to its closed position. Release the throttle first and then release the choke. Disconnect the vacuum hose from the carburetor body and apply a vacuum of at least 10 in.Hg.
- Insert a #4 drill bit between the choke valve and the wall of the air horn.
- Apply sufficient closing pressure to the choke lever to provide a minimum valve opening without distorting the diaphragm link (which connects the choke lever to the vacuum diaphragm). Note that the cylindrical stem of the diaphragm will extend as its internal spring is compressed. This spring must be fully compressed for the proper measurement of the vacuum kick adjustment.
- Remove the drill bit. If a slight drag is not felt as the drill bit is removed, an adjustment of the diaphragm link is necessary to obtain the proper clearance. Shorten or lengthen the diaphragm link by carefully closing or opening the U-bend in the link until the correct adjustment is obtained.
- Refit the vacuum hose to the carburetor body (if it had been removed) and return the fast idle screw to its original location.
- With no vacuum applied to the diaphragm, the choke valve should move freely between its open and closed positions. If it does not move freely, examine the linkage for misalignment or interference which may have been caused by the bending operation. If necessary, repeat the adjustment to provide the proper link operation.
- Hold the throttle valve in the wide open position.
- Insert a 5 / 16 " drill bit between the upper edge of the choke valve and the wall of the air horn.
- With a finger pressing lightly against the choke plate, a slight drag should be felt as the drill bit is being withdrawn.
- If adjustment is necessary, bend the unloader tang on the throttle lever until the correct opening is obtained.
Accelerator Pump and Bowl Vent
- Back off the idle speed adjusting screw.
- Open the choke plate so that, with the throttle plates closed, the fast idle adjusting screw will not contact the fast idle cam.
- Make sure that the pump rod is in the medium stroke hole in the throttle lever and the bowl vent clip on the pump stem is in the center notch.
- Close the throttle plates tightly. It should be [cf2]just possible to insert a 0.060" drill bit (0.050" with Clean Air Package) between the bowl vent and the vent seal.
- If adjustment is necessary, bend the pump rod at the lower angle with a needle-nosed pliers.
Fast Idle Speed
- Warm the engine by driving at least five miles.
- With the engine off and the transmission in Park or Neutral, open the throttle slightly.
- On models without the Clean Air Package, close the choke plate about 20°, then allow the throttle plates to close. The fast idle screw should now rest on the slowest speed step of the cam.
On models with the Clean Air Package, close the choke plate until the fast idle screw can be positioned on the second highest speed step of the cam.
- Start the engine.
- Turn the fast idle speed screw in or out until 700 rpm is obtained.
- Stopping the engine between adjustments is not necessary. However, be sure to position the fast idle speed screw on the cam after each speed adjustment.