LUBRICATION SYSTEM - Continued
Figure 11. Oil Pump Gears.
As the gears revolve, a vacuum is created on the inlet side of the pump and oil is drawn from the oil pan through
the intake screen and pipe assembly into a passage in the crankshaft front cover, which leads to the inlet port in
the pump. The oil then enters the cavities between the gears and the crankshaft front cover. It is then forced out
under pressure through the discharge port into a short gallery in the cylinder block, which leads to the oil cooler
block main oil gallery. At the same time, the oil is directed through a short vertical gallery to the pressure relief
valve, which opens at approximately 105 PSI (724 kPa) to return excess oil to the oil pan.
Oil Pressure Regulator
Stabilized lubricating oil pressure is maintained within the engine at all speeds, regardless of the oil temperature,
by an oil pressure regulator valve. The valve is installed at the end of the vertical oil gallery near the front of the
cylinder block on the side opposite the oil cooler. The oil pressure regulator consists of a valve body, a hollow
piston-type valve, a spring, a spring seat, and a pin to retain the valve assembly within the valve body.
The valve is held on its seat by the spring, which is compressed by the pin in back of the spring seat. The entire
assembly is bolted to the lower flange of the cylinder block and sealed against leaks by a gasket between the
block and the valve body. When conditions are such that the oil pressure at the valve exceeds 50 PSI (345 kPa),
the valve is forced from its seat and oil from the engine gallery is bypassed to the engine oil pan. Thus stabilized
lubricating oil pressure is maintained at all times.
Under normal conditions, the oil pressure regulator should require very little attention. If sludge accumulates in the
lubrication system, the valve may not work freely, thereby remaining open or failing to open at the normal
operating pressure. Whenever the lubricating oil pump is removed for inspection, remove the regulator valve and
spring, and thoroughly clean and inspect them.