Distributor Rotor

A distributor rotor is designed to rotate and distribute the high tension current to the towers of the distributor cap. The firing end of the rotor, from which the high tension spark jumps to each of the cap terminals, should not be worn. Any wear will result in resistance to the high tension spark. The rotor with a worn firing end will have to be replaced. Rotors are mounted on the upper end of the distributor shaft. In this connection, the rotor must have a snug fit on the end of the shaft. On another design, two screws are used to attach the rotor to a plate on the top of the distributor shaft. Built-in locators on the rotor, and holes in the plate, insure correct reassembly. One locator is round; the other is square. The rotor is driven directly by the camshaft, but is "advanced" (turned) by the centrifugal advance mechanism. Advancing the spark timing allows the engine to run efficiently. A vacuum advance is also fitted on some cars for the same reason.