10 of the present invention causes the cylinder valve not shown to open an amount which is progressively proportional to the amount of axial travel of rocker arm push rod 30 at any point in time when the point of contact between the control device 10 and the rocker arm 36 is along the control device first cam like surface 22 the rate of opening of the cylinder valve is directly proportional to the amount of axial travel of the push rod 30 therefore it will be appreciated that during the initial stage of cylinder valve opening and of course as the cylinder valve closes the rate of opening and closing of the cylinder valve is much lower than that obtained by conventional systems employing only rocker arm systems to open and close the cylinder valves it should be noted that the rate of opening of the cylinder valve is greatest when the valve is fully open i e when the point of contact between the control device 10 and the rocker arm force receiving surface 42 is furthest from the control device shaft 14 and rocker arm shaft 38 left most position as shown in drawings those skilled in the art will also appreciate that due to the design of the valve opening control device 10 of the present invention since the point of contact between the control device and the.