A variable-timing valve actuating mechanism for an internal combustion
engine having an axially movable cam shaft, movable by a governor device
to a position proportional to engine rpm. A set of dual cams is provided
for operating intake and exhaust valves with a uniform profile lobe
effective only over an idle to medium rpm range and a non-uniform profile
lobe effective only over a medium to maximum rpm range. A timing gear
drives the cam shaft and utilizes a spiral spine drive to also advance and
retard the cam shaft rotation proportional to the cam shaft axial
position. The variable advance/retard action and the non-uniform cam lobe
are selected to optimize valve overlap, valve opening angle, and valve
timing as a function of rpm.
