In an internal combustion engine using poppet type valves, a center pivot rocker arm is moved through a specific path wherein the roller in contact with a cam is moved to alter the phasing of the valves or injectors in the engine. Depending on the interface between the valve or injector and the rocker arm, the rocker ratio of the rocker arm may be altered, giving a change in lift as well. By positioning a control arm at desired points on either side of a centered position, and rotating the control arm about its own pivot point via an arm actuator, phase change is achieved. The arm actuator controls the location of the control arm and thus the timing of the valve or injector relative to the rotation of the cam. Advanced, centered, and retarded phase change is possible depending upon the movement of the control arm.