Cylinder Head Replacement - GMC G Service Manual

6A6-10 6.2L DIESEL
H Install or Connect (Figures 9 and 10)
Tool Required:
J 26513-A Valve Spring Compressor
1. New valve seal.
2. Valve spring with damper, shield, and cap or rotator.
3. Valve keepers.
• Applying air pressure to the cylinder being ser­
viced, compress the valve spring with J 26513-
A (figure 10).
• Install the valve keepers. Use grease to hold
them in place.
• Carefully release spring pressure. Make sure
the valve keepers remain in place.
• Remove J 26513-A and the air line adapter.
4. Glow plugs.
5. Rocker arm shaft with rocker arms. Refer to "Rocker
Arm, Shaft, and Pushrod Replacement" in this
section.
6. Rocker arm covers. Refer to "Rocker Arm Cover
Replacement" in this section.

CYLINDER HEAD REPLACEMENT

REMOVAL (R/V MODELS) (BOTH SIDES)
M Remove or Disconnect
1. Intake manifold. Refer to "Intake Manifold Replace­
ment" in this section.
2. Injection lines. Refer to DIESEL FUEL INJECTION
(SEC. 6C2).
3. Rocker arm covers. Refer to "Rocker Arm Cover
Replacement" in this section.
• Drain the cooling system.
4. Dipstick tube (left cylinder head).
5. Ground wire at the cowl (right cylinder head).
6. Glow plug relay (left cylinder head).
• Raise the vehicle. Support with suitable safety
stands.
7. Exhaust pipe from the manifold.
• Lower the vehicle.
8. Air conditioning compressor (if equipped); lay aside
(left cylinder head). Refer to AIR CONDITIONING
(SEC. 1B).
9. Generator; lay aside (right cylinder head).
10. Glow plug wires.
11. Rocker arm assemblies and pushrods. Refer to
"Rocker Arm, Shaft, and Pushrod Replacement" in
this section.
] Important
• Rocker arm assemblies and pushrods must be
marked for proper assembly, as outlined
previously.
12. Radiator, bypass and heater hoses.
13. Ground strap.
14. Glow plug temperature inhibit switch connector at the
water crossover pipe.
15. Water crossover pipe/thermostat housing assembly.
16. Cylinder head bolts. Rear bolt in left cylinder head
may have to remain in the head during removal.
17. Cylinder head.
CLEANING AND INSPECTION
• Carbon deposits from combustion chambers.
• All traces of old head gasket from cylinder head and
block. Use of a motorized wire brush is not
recommended.
• Cylinder head bolt threads using a wire brush.
• Metal chips and dirt from the threads in the block.
I M Inspect
• Cylinder head for cracks between the intake and
exhaust ports. Use the magnaflux or dye method if
available.
• Sealing surfaces of the block and cylinder head for
nicks, heavy scratches, or other damage.
• Block for missing or damaged dowel pins, or dowel
pins in the wrong location.
I^ ll Measure
• Cylinder head warpage. If warped more than 0.15
mm (0.006-inch) longitudinally or 0.08 mm (0.003-
inch) transversely, replace the cylinder head. Resur­
facing is not recommended.
• Pre-chamber installed depth. The pre-chamber
should be flush to a maximum of 0.05 mm (0.002-
inch) protrusion.
• Make the measurement at two or more points
on the pre-chamber where the pre-chamber
seats on the head gasket shield and sealing
ring.
• Measure the difference between the flat of the
pre-chamber and the flat surface of the cylinder
head.
• The pre-chamber must not protrude out of the
cylinder head more than 0.05 mm (0.002-inch).
• The pre-chamber must not be recessed into the
cylinder head.
CYLINDER HEAD REPAIR
• Refer to the 1988 Light Duty Trucks Unit Repair
Manual.
INSTALLATION (R/V MODELS) (BOTH SIDES)
H Install or Connect (Figure 11)
1. Head gasket to the block, over the dowel pins.
0
Important
• The block gasket surfaces must be clean.