Abstract: A cam phase adjustor for an internal combustion engine includes a drive gear, an index gear, an actuator and a camshaft. Actuator is rotated and moves linearly to reciprocate the index gear in response to engine rpm changes. Linear movement of the index gear, which serves as the drive link between the drive gear and the camshaft, causes relative rotational motion between the spinning index gear and camshaft, thus changing the angular phase of the camshaft relative to the drive gear. This is used to advance or retard the opening and closing of the intake and/or exhaust valves of an internal combustion engine to improve engine performance over a wide range of operative engine speeds. Linear and rotational movements of the components are facilitated by cooperating grooves and balls in the respective components so there is rolling rather than sliding motion between the components.