Distributor: Description and Operation

Distributor Assembly:

The distributor, mounted to the left end of the cylinder head and driven by the camshaft, directs high voltage ignition coil output to the spark plugs in proper sequence (firing order). To accomplish this, 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.

Inside the distributor, a pick-up coil and igniter are mounted to the breaker plate. A signal rotor (reluctor) 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 vacuum diaphragm, mounted on the side of the distributor and connected to the breaker plate with an operating rod, advances 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.