Distributor Vacuum Unit
Distributor has a double acting (two diaphragms) vacuum unit which operates as follows:
- Advance side of unit is supplied with vacuum from a port in the primary barrel of carburetor, located just above throttle valve. This port does not supply vacuum during idling or during closed throttle deceleration. It supplies full vacuum (to advance timing) at all speeds when the throttle valve is opened enough to uncover port.
- Retard side of unit is supplied with intake manifold vacuum through a line connected directly to intake manifold. During idling and deceleration (when there is no vacuum to advance side of unit) retarded side of unit will cause timing to be retarded about 5°. However, during part throttle operation, when vacuum is supplied to advance side of unit, advance side will overpower retard unit and retard unit will have no effect on timing.