Abstract: In a valve drive system, a plurality of valves are disposed in skewed relation to a cylinder. The valves each are driven by respective rocker arms supported for rotation on a cylinder head via respective rocker pins and cam shafts having three-dimensional cams for engaging these rocker arms. The rocker pins are individually supported on the cylinder head between the cam shafts.

Abstract: In a valve drive system, a plurality of intake or exhaust valves are disposed radially in a cylinder, and the intake or exhaust valves each are driven by respective rocker arms supported for rotation on a cylinder head via a rocker pin and an intake or exhaust cam shaft having three-dimensional cams for engaging these rocker arms. A boss of the rocker arm is coupled to the rocker pin for tilting movement in a direction perpendicular to the axis of the rocker pin. The rocker arm is tiltable with respect to the rocker pin to follow the three-dimensional cam surface. The cam surface can be in line contact with the sliding surface of the rocker arm throughout its circumference.