Abstract: The invention is an improvement upon an engine valve operating mechanism having a cam with a rotational axis and a lobe high point, a movable control surface and a cam follower. In the improvement, the follower has a cam-contacting face and the movable control surface is defined by boundaries maintained to one side of a plane. The plane is generally normal to the cam-contacting face and includes the cam rotational axis. Movement of the control surface varies the time of valve opening and/or closing without increasing the dimension to which such valve is opened. The control surface may be formed on an "insert" (a separate control member which is an adjunct to the conventional valve train components) or as an integral part of the cam follower. In event of a failure involving the insert or follower, the mechanism is fail-safe. The insert or follower may be made of a metal composite material for low inertia and good wear and strength characteristics.

Abstract: The invention is an improvement upon an engine valve operating mechanism having a cam with a rotational axis and a lobe high point, a movable control surface and a cam follower. In the improvement, the follower has a cam-contacting face and the movable control surface is defined by boundaries maintained to one side of a plane. The plane is generally normal to the cam-contacting face and includes the cam rotational axis. Movement of the control surface varies the time of valve opening and/or closing without increasing the dimension to which such valve is opened. The control surface may be formed on an "insert" (a separate control member which is an adjunct to the conventional valve train components) or as an integral part of the cam follower. In event of a failure involving the insert or follower, the mechanism is fail-safe. The insert or follower may be made of a metal composite material for low inertia and good wear and strength characteristics.