Distributor Vacuum Control Valve
PROCEDURE1. With engine at operating temperature and idle speed correctly set, connect a tachometer to the engine.
2. Remove cover from valve and slowly turn the adjusting screw counterclockwise without exerting any inward pressure. After five and no more than six turns, the idle speed should suddenly increase to approximately 1000 rpm.
NOTE: Any more than six turns out will release the compressed spring and washer.
3. If idle speed does not increase after the sixth turn, push inward on the end of the spring and release. Idle speed will increase.
4. After valve has been triggered to the higher rpm, slowly turn the adjusting screw clockwise until idle speed drops back down to proper level. Turn screw one additional turn clockwise.
5. Increase engine speed to 2000 rpm and hold for approximately five seconds then release throttle. The engine should return to idle within four seconds. If not, check return time with dashpot backed off so it does not contact the throttle lever.
6. If the engine still will not return to idle within four seconds, turn the adjusting screw clockwise in one-quarter turn increments until throttle return is satisfactory.
7. If throttle does not return after four one-quarter turn adjustments, the valve is defective and must be replaced.
NOTE: Application of the distributor vacuum control valve and the dual-diaphragm vacuum advance mechanism will vary from vehicle to vehicle.