A number of embodiments of single overhead camshaft five valve per cylinder internal combustion engines. The camshaft and valve operating mechanism is designed so as to permit a compact assembly by placing the camshaft outwardly of the area between the valves. Both direct and rocker arm valve actuation embodiments are disclosed although in the direct valve operating arrangement, rocker arms are employed for operating some of the valves. The valve and bearing arrangement for the camshaft permits the cam lobes to be positioned closely adjacent each other to maintain compactness of the engine design. In all embodiments, a central spark plug position is accommodated and the spark plug extends generally parallel to the axis of the associated cylinder bore.