GMC T Series 1994 Repair Manual page 414

ENGINE LUBRICATION
Lubrication schematics are shown in figures 5 and 6.
The gear-type oil pump is driven from the distributor
shaft, which is gear driven from the camshaft. Oil is
drawn into the oil pump through a pickup screen and
pipe.
Pressurized oil is routed to the oil filter. In case of
excessive oil pressure a bypass valve is provided. Fil­
tered oil flows into the main gallery and then to the
Figure 5— Engine Lubrication Diagram
camshaft, balance shaft rear bearing, and crankshaft
bearings. The valve lifter oil gallery supplies oil to the
valve lifters. Oil flows from the hydraulic lifters through
the hollow pushrods to the rocker arms. Oil from over­
head drains back to the crankcase through oil drain
holes.
The timing chain is drip fed from the front camshaft
bearing. The pistons and piston pins are lubricated by
oil splash.
V0503