Valve operating system for an automotive engine

A valve operating system for an automotive engine having intake valves and exhaust valves, a cam shaft having cams, and rocker arms rocked by the cams to operate the valves, the system comprising:

• at least one of the cams including a first cam and a second cam which are different in shape of contour;
• the first cam having a base circle, the diameter of which is equal to that of a base circle of the second cam;
• one of the rocker arms including a first rocker arm engaging with the first cam and a second rocker arm engaging with the second cam;
• the first and second rocker arms being rotatably engaged with each other so as to be independently rocked by the first and second cams, respectively;
• first means on at least one of the first and second rocker arms for selectively engaging the first and second rocker arms with each other, at a position where both the rocker arms engage with the base circles of both the cams, so as to be rocked together by the second cam;
• second means including hydraulic means for acting on said first means so that the latter engages and respectively disengages both the first and second rocker arms;
• a hydraulic circuit for supplying oil to the second means for operating the second means;
• the hydraulic circuit including valve means provided in the cam shaft for supplying the oil to the second means at a time when both the rocker arms engage with the base circles at the same time to engage both rocker arms with each other so as to be rocked together by the second cam.