into the oil pump housing. The oil pump drive gear shaft is supported by the tach drive housing on one end and the oil pump housing at the opposite end. The oil pump drive gear has a tachometer drive gear attached to its end which drives a tachometer shaft gear inside the tach drive housing for either electrical or mechanical tachometers. As the engine starts rotating, the oil pump drive gear turns counterclockwise (looking from the rear of the engine forward); this drives the driven gear in a clockwise direction. The two gears turning create a suction that draws oil from the sump, through the oil suction tube to the pump gears. The oil is then forced around the outside of the gears and directed through a gallery to the oil filter adapter and pressure relief valve.
Oil that flows past the pressure relief valve is directed through a passage back to the inlet side of the pump gears. The oil pressure relief valve limits oil pressure to a predetermined value; this ensures adequate lubrication to the engine and its accessories a high engine RPM. Oil pressure is adjusted by turning the oil pressure relief valve adjusting screw.
The oil filter incorporates a by-pass in the event that the filter element becomes clogged. During normal operation oil, flows from the by-pass to an area between the oil filter housing and filter element. The oil is then directed through the element and down a gallery in the filter adapter through a passage in the oil pump housing and out to the engine.
The foregoing information provided courtesy of Kori Ibey of Maximum North Aviation.