Abstract: A two cycle internal combustion piston engine is provided with cam controlled inlet valves, as well as exhaust valves, disposed in the head of the engine cylinder. The two cycle engine can perform with an expansion ratio greater than the compression ratio. A standard two cycle internal combustion piston engine can be converted to the inventive two cycle engine construction by replacing the conventional engine cylinder head, replacing the conventional engine valve cam shaft, and directing air flow in the intake manifold to one side of the replacement cylinder head.