Abstract: A method of assembling a valve driving mechanism, having a variable valve timing unit incorporated in a cylindrical mounting base, to a dual overhead camshaft engine. The engine has camshafts which are rotatably connected by camshaft gears. The method includes the initial step of mounting one camshaft gear, maintained at a predetermined angular position relative to the other camshaft gear attached to the other camshaft, and a lock nut on the one camshaft. Subsequent steps include first adjusting the angular position of the mounting base relative to the one camshaft gear and then the angular position of the variable valve timing unit relative to the one camshaft, and fastening the one camshaft gear to the mounting base by the lock nut and, simultaneously, the variable valve timing unit to the one camshaft.

Abstract: A valve driving mechanism for a double overhead camshaft engine includes a camshaft drive mechanism, including a camshaft sprocket for transmitting engine output from a crankshaft of the engine to one of intake and exhaust camshafts. A valve timing varying mechanism is driven so as to vary a valve timing of, for example, a set of intake valves relative to a valve timing of a set of exhaust valves. The valve timing varying mechanism includes a first helical gear, mounted on the exhaust camshaft for rotation, a second helical gear, in mesh with the first helical gear, which is rigidly secured to the intake camshaft, and a cylindrical sliding element, mounted on the exhaust camshaft for axial displacement. The cylindrical sliding element operationally couples the exhaust camshaft to the camshaft drive mechanism so as to cause a relative rotational displacement therebetween when the cylindrical sliding element undergoes axial displacement with respect to the exhaust camshaft.

Abstract: A cylinder head structure for a V-type engine comprising a pair of cylinder head members which are the same in shape and oriented in opposite directions and which are provided in each of the front and rear end wall portions with an opening. Camshafts are supported for rotation in the respective cylinder head members so that their respective one ends project outside through the openings on the same end of the engine. A cam pulley is mounted on the projecting portion of each cam shaft, and a transmission belt is provided for transmitting the driving force of the crankshaft to the cam pulley on each camshaft. A pair of first cover members are mounted on the end wall portions of the respective cylinder head members through which the camshafts project to form closed cross section spaces together with the corresponding cylinder head members for covering the transmission belt.