Abstract: An internal combustion engine is provided which includes an improved exhaust valve, air/fuel injector, and timing system for operating the valves and injectors. The exhaust valve comprises a rotatable cylindrical valve body having a passage which is located in an exhaust passage. The valve body is actuated by linkage connected to an electronically controlled solenoid. The air/fuel injector comprises a housing having air and fuel reservoirs having orifices therein and an air and fuel needle for selective location each the respective orifices. Air and fuel passing through the orifices is mixed in a venturi and then passes through a screen and check valve into the cylinder. The timing mechanism is connected to the injector and valve and comprises a drum which rotates a housing. Sensors in the housing detect passage of an element on the drum, completing a circuit which actuates an exhaust valve solenoid or the injector needles.