Nova/Chevy II L4-1600cc 4ALC Nummi (1988)
Vacuum Spark Delay Valve: Description and Operation
Distributor Spark Vacuum Retard Delay Valve (DS-VRDV)
This valve is used with a thermal switch that connects the chamber halves (ports 2 and 3) after engine warm-up. When the engine is cold, this valve
delays the distributor retard during quick throttle openings. When the engine is warm, the thermal vacuum switch allows the advance unit to respond
directly to ported vacuum changes when the TVS bypasses the delay valve.