Dual Diaphragm Distributor: Description

The dual diaphragm unit consists of two independently operating diaphragms. The outer (primary) diaphragm utilizes carburetor ported vacuum to advance ignition timing. The inner (secondary) diaphragm is actuated by intake manifold vacuum to provide ignition timing retard during periods of closed throttle operation. This retarded timing aids in the reduction of hydrocarbon emissions.