This paper deals with the development of a system to control the inlet-valve-timing of a single - cam gasoline engine. With this scheme the camshaft can be phased continuously to any position within 60 crank degree range by an electronic control unit to reflect changes in engine operating conditions. A control strategy was established which would optimize power at wide -open throttle and minimize emissions at small throttle openings. For this system, a mechanical self-protection device and a fail -safe system have been developed. Development testing has shown that with the proper control strategies, the power, emission, and idle quality of the engine can all be improved.