Abstract: Within the cylinder head of an internal combustion engine, a rotatively mounted disc valve having beveled gear teeth upon the edge of its outer perimeter and a plurality of equally spaced ports about its center of rotation for cyclic indexing with a like number of sets of exhaust and intake conduits within the said cylinder head leading from the combustion chamber to respective exhaust and intake manifolding. The disc valve completes one whole revolution for every eight revolutions of the crankshaft of said internal combustion engines.