Fast Idle Cam Position
- 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 000031 pressure on the choke linkage.
- Insert a 0.110" drill bit between the upper edge of the choke plate and the wall of the air horn.
- If adjustment is necessary, bend the fast idle link at the angle until the specified drill 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 15 in.Hg.
- Insert a 0.150" 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 or gauge 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 0.170" 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- With a finger pressing lightly against the choke plate, a slight drag should be felt as the drill is being withdrawn.
- If adjustment is necessary, bend the unloader tang on the throttle lever until the correct opening is obtained.
Accelerator Pump Stroke
- Make sure that the pump connector rod is in the first slot (next to the retaining nut) of the pump arm.
- Measure the travel (drop) of the accelerator pump plunger between curb idle, or closed throttle, and wide open throttle. Travel should be 0.260" for curb idle-to-wide open throttle, or 0.310" for closed throttle-to-wide open throttle.
- If not, bend the pump operating rod at the angle to adjust.
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. Remove the air cleaner and disconnect the vacuum lines to the heated air control and the OSAC (Orifice Spark Advance Control) valve. If there is no OSAC valve, disconnect the distributor vacuum advance line. Disconnect the EGR hose. Cap all carburetor vacuum fittings.
- 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 the speed of 1,700 rpm for manual transmission or 1,800 rpm is reached.
- 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.
Vacuum Throttle Positioner
- Run the engine to normal operating temperature.
- With the transmission in Neutral and the brakes applied, accelerate the engine to above 2,000 rpm. Note that the vacuum positioner unit operates and can withstand a hand-applied load in the operating position. If not, replace the positioner.
- Accelerate the engine, by hand-moving the linkage, to 2,500 rpm.
- Loosen the positioner adjustment locknut and rotate the positioner assembly until the positioner just contacts the throttle lever.
- Release the throttle lever and slowly adjust the positioner to decrease the engine speed until a sudden drop in engine speed occurs, above 1,000 rpm. At this point, continue turning the positioner, in the decreasing direction, an additional 1 / 4 turn. Hold the positioner and tighten the locknut.
- Accelerate the engine, by hand, to 2,500 rpm and release the throttle. The engine should return to normal idle.
- Invert the air horn so that the weight of the float alone is forcing the needle against the seat.
- Measure the clearance between the top of the float and the float stop. The clearance should be 0.080".
- If an adjustment is necessary, bend the flat tab toward or away from the needle using a narrow blade screwdriver.
- Check the float drop by holding the air horn in an upright position. The bottom edge of the float should be even with and parallel to the underside surface of the air horn. If necessary, bend the tang on the float arm to make an adjustment.