Abstract: A spark timing control system for an internal combustion engine. The spark timing of the engine is controlled by a signal generating device driven in synchronism with the engine which develops signals that represent engine crankshaft position. The signal generating device has mechanisms for phase shifting the signal as a function of engine speed and engine manifold vacuum. The system includes a spark timing controller connected to the signal generating device which is capable of retarding spark timing from that set by the signal generating device in a plurality of crankshaft angle steps. The ignition timing provided by the spark timing controller is controlled by an electronic spark selection device which responds to engine operating parameters such as engine speed, engine manifold vacuum and engine temperature.