Bosch Rotor Arm

Fits:
Porsche 924 1977-85

The "rotor" head is attached to the top of the distributor shaft which is driven by a gear on the engine's camshaft and thus synchronized to it. This rotor is pressed against a carbon brush on the center terminal of the distributor cap which connects to the ignition coil either through the top and wired directly to the coil in HEI systems, or via the center terminal in points ignition systems and remotely connected to the coil.

The rotor is constructed such that the center tab is electrically connected to its outer edge so that voltage coming in to the center post travels through the carbon point to the outer edge of the rotor. As the camshaft rotates, the rotor spins and its outer edge passes each of the internal plug terminals to fire each spark plug.