Cam-in-block

   The camshaft is located within the engine block, and operates directly on the valves，or indirectly via pushrods and rocker arms. Because they often require pushrods they areoften called pushrod engines.

    In this arrangement，the cam lobs push against round metal cylinders called followerupward. The cam follower rides against a push rod, which pushes against a rocker arm.The rocker arm pivots on a shaft through its center. As one side of the rocker arm movesup，the other side moves down, just like a seesaw. The downward-moving side of therocker arm pushes on the valve stem to open the valve.

    Because a push-rod valve train has additional parts，it is more difficult to run at highspeeds. Push-rod engines typically run at slower speeds and, consequently, produce lesshorsepower than overhead camshaft design of equal size.