GMC 1990 Light Truck Repair Manual page 476

6A4-4 4.8 LITER L6
1
. Oil Cap
2
. Clip
3. Screw
4. Reinforcement
5. PCV Valve
6
. Seal
7. Rocker Arm Cover
8
. Gasket
9. Grommet
10
. Connector
11
. Nut
12
. Ball
13. Rocker Arm
14. Rocker Arm Stud
15. Valve Key
16. O-ring Seal
17. Rotator
18. Shield
19. Seal
20
. Valve Spring
TOOLS AND SHOP EQUIPMENT
A clean, well lit work area should be available. Other
necessary aids include: A suitable parts cleaning tank,
compressed air supply, trays to keep parts and fasteners
organized, and an adequate set of hand tools.
An approved engine repair stand will aid the work and
help prevent personal injury or damage to engine
compartments.
Special tools are illustrated throughout this section, and
are listed at its end. These tools (or their equivalents) are
specially designed to quickly and safely accomplish the
operations for which they are intended. The use of these
tools will also minimize possible damage to engine
components.
Some precision measuring tools are required for
inspection of certain critical components. Torque
wrenches will be necessary for correct assembly of
various parts.
ACCESSORY REMOVAL
This manual assumes that the engine accessories have
been removed. These accessories may include one or
more of the following:
Hydraulic Pump
Generator
Distributor
DISASSEMBLY
21
. Pushrod
22
. Bolt
23. Bolt
24. Washer
25. Bracket
26. Cylinder Head
27. Gasket
28. Stud
29. Washer
30. Nut
31. Intake Manifold
32. Nut
33. Head Gasket
34. Clamp
35. Bolt
36. Gasket
37. Exhaust M anifold
38. Stud
39. Bolt
40. Washer
Figure 3—Cylinder Head, Manifolds, and Components
AIR Pump
Cooling Fan
Carburetor
42. Intake Valve
43. Exhaust Valve
44. Switch
45. Plug
46. Clamp
47. Hose
48. Nipple
49. Gasket
50. Housing
51. Bolt
52. Therm ostat
53. Gasket
54. Water Outlet
55. Bolt
56. Stud
57. Washer
58. Bracket
59. Stud
It is beyond the score of this manual to detail the many
different accessory installations. Refer to the proper Truck
Service Manual for this information.
Diagrams of emission and vacuum hose routings,
wiring harness routings, accessory drive belt layout, etc.,
should be made before removing accessories.
CLEANING
Remove the engine accessories before cleaning to
provide better access to engine exterior surfaces. After
removing the carburetor, distributor, fuel pump, oil filter,
etc., cover the openings with tape to prevent the entry of
water, solvent, and dirt.
Methods used to clean the engine will depend on the
aids which are available. Steam cleaning, pressure
washing, or solvent cleaning are some acceptable
methods. Allow the engine to dry before beginning the
work.
It is important that the engine be as clean as possible to
prevent d irt from e n te ring c ritic a l areas during
disassembly.
PARTS IDENTIFICATION
Refer to figures 3 through
41. Stud
B-07995
6
.