GMC 1989 Light Duty Truck Repair Manual page 428

6A3-4 4.3 LITER V-6
A. Regulator Valve (Shown In Open Position)
B. Suction
C. Oil Pressure Switch
D. Valve Lifter Gallery
E. Main Oil Gallery
F. Bypass Valve
Front View
Front View Rear View
Showing Path Of Oil To Tinning Chain. Showing Main Gallery, Oil Filter And Crankshaft Oil Feed.
F-05526
Figure 2— Engine Lubrication Diagram
L i _ _ _ -------- . -