An overhead rotary valve fitted into a cylinder head with diametrical polygonal openings formed therein for use in combination with an internal combustion engine, driven to bring intake and exhaust ports into and out of alignment with passages leading to and from the combustion chamber. Sleeve bearings are fitted in the cylinder head that provide surface sealing, and annular sealing members prevent the air/fuel mixture or exhaust gases from flowing into regions intermediate ports and individual cylinders. Utilizing this overhead rotary valve and associated seals and bearings increases the efficiency and performance of an internal combustion engine. The overhead rotary valve rotating, at one quarter the speed of the crankshaft, minimizes wear and noise levels, self cleans the ports, allows the engine to operate at higher rpm and imparts proper opening and closing of passages at the proper sequence of valve timing without concern of valve float. The instant invention removes the need for reciprocating intake and exhaust valves, camshafts, rocker arms, lifters, push rods, valve guides and retainers, and other related hardware for actuation, significantly increasing the reliability and effectiveness of the internal combustion engine, while reducing overall manufacturing costs.