Delay Valve
Connect tachometer and timing light to engine. Start engine and allow to idle. Quickly open throttle valve and let engine run at 3000 RPM. Check ignition timing. The delay valve should open after 4-8 seconds (ignition timing should advance). If not, replace delay valve.
NOTE:
The White end of delay valve should be toward the vacuum control unit of the distributor. Also make sure that the shorter hose is between the valve and the vacuum control unit of the distributor.