A valve timing control system for an internal combustion engine is provided. This system comprises a sprocket assembly connected to a crankshaft of the engine, a camshaft assembly connected to the sprocket assembly for driving intake and/or exhaust valves of the engine, a ring gear assembly disposed between the sprocket assembly and the camshaft assembly, and a fluid power source for providing fluid pressure to a pressure chamber to axially displace the ring gear assembly to vary a phase angle relation over a range of first to second phase angles. A fluid pressure supply and drain lines are defined in the system which communicates between the fluid power source and the pressure chamber and between the pressure chamber and a drain port of the system respectively. The system further includes a solenoid operated directional control valve which is responsive to a control signal from a controller to selectively block the fluid pressure supply or drain lines according to variation in engine operating conditions for varying the valve timing.