Distributor: Description and Operation

Distributor Assembly:

PURPOSE
Directs high voltage ignition coil output to spark plugs in proper sequence (firing order). A rotor on the driven shaft acts as a rotary contact, directing ignition coil voltage to each spark plug terminal as it turns inside the distributor cap.

LOCATION
Left end of cylinder head.

OPERATION
Inside the distributor, a pick-up coil/igniter assembly is mounted to the breaker plate. A signal rotor on the driven shaft turns past the pick-up coil, triggering the igniter to interrupt the coil primary ground connection each time a spark plug is to fire.

Two mechanisms control spark advance. A two-chamber vacuum diaphragm, mounted on the side of the distributor and connected to the breaker plate with an operating rod, advances and retards timing according to engine load sensed as manifold vacuum. To advance timing with relation to engine speed (rpm), the distributor incorporates a centrifugal advance device. As engine speed increases, two governor weights controlled by calibrated springs are forced to move outward, causing the rotor shaft to move ahead of the main distributor shaft and advance the timing.