A torque amplifying camshaft for operating a valve of each of a plurality valves of an internal combustion engine, the camshaft having an elongagte shaftlike portion and an engine valve operating cam for each of the valves, the valve operating cams being spaced apart from one another along the shaftlike portion. Each of the engine valve operating cams has an outwardly projecting portion, and the outwardly projecting portions are circumferentially offset from one another about the longitudinal central axis of the camshaft. The camshaft also carries a supplementary cam surface, either in the form of an outwardly facing surface of a separate supplementary cam or an inwardly facing surface of a portion of a drive sprocket which is keyed to the shaftlike portion. The supplementary cam surface is adapted to be followed by a spring biased supplementary cam follower and has portions which introduce torque pulses into the camshaft which are synchronous with and consistently directed with respect to the torque pulses that are introduced into the camshaft by the engagement between the valve operating cams and spring biased followers which engage such valve operating cams.