Deceleration Valve: Service and Repair

CONTROL VALVE, ADJUST

1. Disconnect valve to carburetor hose at carburetor and connect to an external vacuum source equipped with a vacuum gauge, then disconnect valve to actuator hose at actuator and connect to vacuum gauge.
2. Firmly place finger over end of bleed fitting and apply minimum of 23 inches Hg vacuum to the control valve. Seal off the vacuum source, then uncover the bleed fitting. The vacuum reading on the actuator side will drop off to zero and the reading on the vacuum source gauge will drop to a value designated as the ``valve set point''. If this value is not 21.5 ± .50 inches Hg for V8-350 or 21 ± .50 inches Hg for V8-454, the valve must be adjusted as follows.
a. To adjust the valve, pry off the plastic cover and turn the screw clockwise to raise the set point or counterclockwise to lower the set point and recheck setting. If the valve cannot be adjusted, it must be replaced.

THROTTLE LEVER ACTUATOR, ADJUST

1. Disconnect valve to actuator hose at valve and connect to an external vacuum source equipped with a vacuum gauge.
2. Check throttle lever, shaft and linkage for freedom of operation.
3. Run engine until operating temperature is reached and idle is stabilized with transmission in neutral or park.
4. Apply 20 inches Hg vacuum to actuator, then open throttle slightly and allow to close against extended actuator plunger. Note engine speed.
5. If speed noted above is not within 1475-1525 RPM for V8-350 engines, or 1375-1425 RPM for V8-454 engines, turn the actuator screw in or out as necessary to obtain the desired TRC speed range and repeat step 4, and readjust if necessary.