The lubrication system consists of the suction tube, oil pump, cooler, filters, internal engine passages and the oil pan. The pan can be turned end-for-end to provide either a front or rear sump. The dipstick placement and suction tube length correspond with sump location. A longer suction tube and support is required when the pan is positioned for a rear sump.
The oil pump draws lubricant from the sump and forces it through the oil cooler, oil filters, and then into the oil manifold. Oil flows through connecting passages to lubricate the engine components. A bypass valve in the pump controls the maximum pressure of the oil from the pump.
As oil temperature increases, oil viscosity and pressure decreases and the oil filter bypass valve closes. Now, only filtered oil is delivered to the engine components. Oil temperature continues to increase and the oil cooler bypass valve closes. Oil now flows through the oil cooler and oil filter before reaching the engine components.
A contaminated or restricted oil filter element will not prevent lubricating oil from being delivered to the engine components. The oil filter bypass valve will open, allowing oil to bypass the filter element.
An oil manifold, cast into the cylinder block, directs lubricant to the camshaft journals and main bearing supply passages. Oil is also directed up through the cylinder head to lubricate the valve rocker arm shafts.
The connecting rod bearings receive oil through drilled passages in the crankshaft between the main bearing journals and connecting rod journals.
When the engine is warm and running at rated speed, the oil pressure gauge should register in the "operating range" (58 to 72 psi). A low pressure reading is normal at idling speeds.
Some engines may be equipped with an auxiliary or remote mounted by-pass filter system. This system must be connected so part of the oil continuously circulates through the by-pass filter, from the crankcase lubricating oil pump. An orifice on the outlet or clean side of the filter restricts the flow of oil through the by-pass filter so that full oil pressure is available to all parts of the engine. Filtered oil from the by-pass filter is returned to the crankcase sump. The by-pass filter must never be used in place of the factory installed full flow filter.