cam body 33 and therefore rotate with the cam body 33 the precise manner of fixing the guide rod 65 with the cam body 33 can vary including the use of tabs and keyway grooves or any other convenient method in the preferred embodiment the guide rod 65 is able to be moved longitudinally within the cam body 33 a helical slot 71 is formed in the guide rod 65 and accepts the drive lug 61 by the cam rod 65 shifting in a longitudinal direction with respect to the cam body 33 the drive lug 61 becomes positioned at different portions of the helical slot 71 the drive lug 61 remains longitudinally fixed to the cam body 33 due to the fact that the cams 47 are restrained in their longitudinal movement by the flanges 51 52 consequently the cams 47 are unable to shift longitudinally with the guide rod 65 since the drive lug 61 on each of the unit injector cams 47 fit within the slots 71 longitudinal movement of the drive rod 65 causes the cams 47 to change their angular positions with respect to the cam body 33 thus movement of the guide rod 65 in one direction causes the relative location of the slot 71 as it appears at the opening between the end walls 55 56 to shift the drive lug 61 rests in the slot 71 so that a shift in this relative position caused by a longitudinal shift in the.