Abstract: A valve mechanism of an internal combustion engine is of a type which has at least two cams for each intake (or exhaust) valve. One cam is shaped to allow the associated engine to exhibit a marked fuel saving characteristic and the other cam is shaped to also the engine to produce a higher torque at relatively low (or high) engine speed. Upon a cam switching between these cams, at least one of the cams is subjected to a phase change before and/or after the actual cam switching. As a result, the undesired shock at the cam switching is eliminated or at least minimized.

Abstract: A double overhead camshaft engine having two camshafts rotatably supported by a cylinder head. This two camshafts are drivably connected through an idler gear with a crankshaft of the engine by means of drive chains. The idler gear is rotatably mounted on an idler gear installation bolt which is fixedly secured only to a front end section of the cylinder head in a so-called cantilever arrangement. A surrounding wall structure for the idler gear is formed integral with the front end section of the cylinder head and extends in the direction of axis of the idler gear over the idler gear to form a front end section. An opening is formed at the surrounding wall structrure front end section and located on an opposite side of the cylinder head front end section with respect to the idler gear. The opening is closed with a cover which is disposed spaced from the idler gear installation bolt, so that no connection is made to the idler gear and the installation bolt therefor.