Abstract: A longitudinally slidable cam shaft means for use with an automotive power system having improved efficiency and low pollution characteristics. The drive motor operates only when power to the wheels is desired and includes variably opening valves controlled by the cam shaft means. The axially sliding cam shaft controls the valves which may be opened by varying amounts to control the speed and direction of rotation of the drive motor. Regenerative braking is provided by the drive motor and by reversing the direction of rotation of the cam shaft, the valves act to send compressed gas to the combustion chamber.