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Home >> GMC >> 1978 >> Forward Control 5.7L Eng VIN L, Automatic Trans, Trans Mfr CD 400/M40 >> Repair and Diagnosis >> Engine Performance >> Ignition System >> Vacuum Advance Spark Control >> Description >> Spark Control Switch

Spark Control Switch

The spark control switch system is used on 350" and 400" V8 engines with Heavy Duty emissions. It is installed between the TVS check valve and the distributor.