hydraulic head 16 includes a central vertical bore 108 within which a pumping and distributing plunger 110 is slidably and rotatably disposed the bore 108 which passes completely through the hydraulic head 16 is closed at its upper end by a plug 112 sealed therein by seal ring 114 and secured by the screw 116 a fuel pumping chamber 118 is formed within the bore 108 between the top of the plunger 110 and the plug 112 the plunger 110 is actuated by a camshaft 120 driven by the engine on which the pump is mounted the camshaft includes a cam 122 which engages a roller 134 of tappet 136 abutting the lower end of the plunger compression spring 138 holds the plunger and tappet against the cam the rotation of the camshaft 120 will accordingly produce a reciprocatory movement of the plunger 110 by means of the cooperation of the cam 122 tappet 136 and spring 138 the rotation of the plunger 110 is also produced by the rotating camshaft 120 which is geared to a governor shaft 140 a gear 142 on the camshaft 140 meshes with a face gear 144 having a hub portion 146 which is slidably keyed to the lower end of the plunger to produce rotation of the plunger while permitting a reciprocatory movement of the plunger with respect thereto since the present pump is designed to supply fuel to a six cylinder engine there will be six axial pumping strokes of the plunger 110 for each plunger revolution the plunger will accordingly rotate 60 u00b0 during each pumping cycle the low pressure.