Vacuum Control Valve
With engine at normal operating temperature, ignition timing and hot (slow) idle speed correctly set, dashpot stem not touching throttle lever, proceed as follows:
- Connect tachometer to engine, connect vacuum gauge to distributor vacuum tube, then clamp vacuum tube between vacuum valve and manifold. Disconnect distributor vacuum tube at distributor and clamp tube shut. Connect a vacuum gauge (0-30" of mercury) to the distributor vacuum tube. The tee fitting should have the same inside diameter as the distributor vacuum tube.
- Adjust carburetor to obtain the specified engine speed and exhaust emission level. The distributor vacuum must be below 4" of mercury at idle. Remove the clamps from the vacuum tubes and reconnect-vacuum tube to the distributor. Remove vacuum valve cover.
- Speed engine up to 2000 RPM in neutral and hold speed for approximately 5 seconds. Release throttle and observe distributor vacuum. When the throttle is released, the distributor vacuum should increase to above 16" of mercury and remain there for a minimum of I second. The distributor vacuum must fall below 4" of mercury within 3 seconds after the throttle is released.
- If vacuum control valve operation is not correct, adjust as directed under Service Procedures above.