Forward & Reverse Delay Valves

The forward and reverse delay valves are one-way check valves used in the vacuum advance signal circuit to control speed and direction of vacuum advance signals sent to distributor. These aid in driveability and in lowering hydrocarbon emissions.

The forward delay valve allows a gradual advance signal to distributor. The reverse delay valve does not allow advance signal to bleed out of distributor advance unit (cold engine) during acceleration. This holds distributor in full advance mode until CTO switches to ported vacuum after engine warms up.