Holley 4000

	Holley 4000 Instruction Sheets Holley 4000 Visual Instruction Manual Holley 4000 1955 Newsletter

What Does The Spark Control Valve Do?
The spark control valve in the passage from the throttle bore provides
an efficient degree of spark advance during periods of acceleration by
momentarily providing a partially retarded spark. This partially retarded
spark minimizes detonation, or pinging and increases engine responsiveness
while accelerating. In effect, the spark valve provides an intermediate
spark advance curve between a fully retarded spark and the normal spark
advance which would be excessive when the engine is suddenly accelerated.
The spark control valve accomplishes this by controlling the manifold
vacuum admitted to the distributor vacuum
line.