Variable valve timing mechanism for engine

An internal combustion engine variable valve timing mechanism comprised of a cylinder head assembly defining a bearing surface for directly engaging and journaling a corresponding bearing surface of a camshaft, said camshaft having a portion that extends on one side of said engine body bearing surface, a hydraulically operated, variable valve drive element for changing the phase angle between the camshaft and a camshaft drive element associated with said camshaft portion, a hydraulic conduit extending through said cylinder head assembly for supplying controlled hydraulic actuating fluid to the hydraulically operated variable valve drive element, a segment of said cylinder head assembly bearing surface being formed by a separate engine body element that is detachably connected to a main cylinder head element and in which a portion of said hydraulic conduit is formed, a bearing member affixed to said separate engine body element and defining a remaining segment of cylinder head assembly bearing surface for directly engaging and journaling the corresponding bearing surface of the camshaft in cooperation with said engine body bearing surface segment, and an operating valve for controlling the supply of hydraulic fluid through said hydraulic conduit, said operating valve being mounted in said separate engine body element.