Hummer H2. Manual - part 60

Manual removal of deposits may be required prior to bead blasting, followed by some other cleaning method. 
Carbon, paint and rust may be removed using bead blasting method. Components must be free of oil and grease 
prior to bead blasting. Beads will stick to grease or oil soaked areas causing area not to be cleaned.  

Use air pressure to remove all trapped residual beads from component after cleaning. After cleaning internal 
engine parts made of aluminum, wash thoroughly with hot soapy water. Component must be thoroughly cleaned 
as glass beads will enter engine oil resulting in bearing damage.  

CHEMICAL CLEANING 

Solvent tank is used for cleaning oily residue from components. Solvent blasting sprays solvent through a 
siphon gun using compressed air.  

The hot tank, using heated caustic solvents, is used for cleaning ferrous materials only. DO NOT clean 
aluminum parts such as cylinder heads, bearings or other soft metals using the hot tank. After cleaning, flush 
parts with hot water.  

A non-ferrous part will be ruined and caustic solution will be diluted if placed in the hot tank. Always use eye 
protection and gloves when using the hot tank.  

Use of a cold tank is for cleaning aluminum cylinder heads, carburetors and other soft metals. A less caustic and 
unheated solution is used. Parts may be left in the tank for several hours without damage. After cleaning, flush 
parts with hot water.  

Steam cleaning, with boiling hot water sprayed at high pressure, is recommended as the final cleaning process 
when using either hot or cold tank cleaning.  

COMPONENT CLEANING 

SHEET METAL PARTS 

Examples of sheet metal parts are rocker covers, front and side covers, oil pan and bellhousing dust cover. Glass 
bead blasting or hot tank may be used for cleaning.  

Ensure all mating surfaces are flat. Deformed surfaces should be straightened. Check all sheet metal parts for 
cracks and dents.  

INTAKE & EXHAUST MANIFOLDS 

Using solvent cleaning or bead blasting, clean manifolds for inspection. If intake manifold has an exhaust 
crossover, all carbon deposits must be removed. Inspect manifolds for cracks, burned or eroded areas, corrosion 
and damage to fasteners.  

Exhaust heat and products of combustion cause threads of fasteners to corrode. Replace studs and bolts as 
necessary. On "V" type intake manifolds, sheet metal oil shield must be removed for proper cleaning and 
inspection. Ensure all manifold parting surfaces are flat and free of burrs. 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Engine Overhaul Procedures

  

CYLINDER HEAD REPLACEMENT 

REMOVAL 

Remove intake and exhaust manifolds and valve cover. Cylinder head and camshaft carrier bolts (if equipped) 
should be removed only when engine is cold. On many aluminum cylinder heads, removal while hot will cause 
cylinder head warpage. Mark rocker arm or overhead cam components for location.  

Remove rocker arm components or overhead cam components. Components must be installed in original 
location. Individual design rocker arms may utilize shafts, ball-type pedestal mounts or no rocker arms. For all 
design types, wire components together and identify according to corresponding valve. Remove cylinder head 
bolts. Note length and location. Some applications require cylinder head bolts be removed in proper sequence to 
prevent cylinder head damage. See Fig. 1 . Remove cylinder head.  

INSTALLATION 

Ensure all surfaces and head bolts are clean. Check that head bolt holes of cylinder block are clean and dry to 
prevent block damage when bolts are tightened. Clean threads with tap to ensure accurate bolt torque.  

Install head gasket on cylinder block. Some manufacturers may recommend sealant be applied to head gasket 
prior to installation. Note that all holes are aligned. Some gasket applications may be marked so that certain area 
faces upward. Install cylinder head using care not to damage head gasket. Ensure cylinder head is fully seated 
on cylinder block.  

Some applications require head bolts be coated with sealant prior to installation. This is done if head bolts are 
exposed to coolant passages. Some applications require head bolts be coated with light coat of engine oil.  

Install head bolts. Head bolts should be tightened in proper steps and sequence to specification. See Fig. 1 . 
Install remaining components. Tighten all bolts to specification. Adjust valves if required. See VALVE 
ADJUSTMENT.  

NOTE:

Some manufacturers require that head bolts be retightened after specified 
amount of operation. This must be done to prevent head gasket failure. 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Engine Overhaul Procedures

  

Fig. 1: Typical Cylinder Head Tightening or Loosening Sequence 

VALVE ADJUSTMENT 

Engine specifications will indicate valve train clearance and temperature at which adjustment is to be made on 
most models. In most cases, adjustment will be made with a cold engine. In some cases, both a cold and a hot 
clearance will be given for maintenance convenience.  

On some models, adjustment is not required. Rocker arms are tightened to specification and valve lash is 
automatically set. On some models with push rod actuated valve train, adjustment is made at push rod end of 
rocker arm while other models do not require adjustment.  

Clearance will be checked between tip of rocker arm and tip of valve stem in proper sequence using a feeler 
gauge. Adjustment is made by rotating adjusting screw until proper clearance is obtained. Lock nut is then 
tightened. Engine will be rotated to obtain all valve adjustments to manufacturer's specifications.  

Some models require hydraulic lifter to be bled down and clearance measured. Push rods of different length can 
be used to obtain proper clearance. Clearance will be checked between tip of rocker arm and tip of valve stem in 
proper sequence using a feeler gauge.  

Overhead cam engines designed without rocker arms actuate valves directly on a cam follower. A hardened, 
removable disc is installed between the cam lobe and lifter. Clearance will be checked between cam heel and 
adjusting disc in proper sequence using a feeler gauge. Engine will be rotated to obtain all valve adjustments.  

On overhead cam engines designed with rocker arms, adjustment is made at valve end of rocker arm. Ensure 
valve to be adjusted is riding on heel of cam on all engines. Clearance will be checked between tip of rocker 
arm and tip of valve stem in proper sequence using a feeler gauge. Adjustment is made by rotating adjusting 
screw until proper clearance is obtained. Lock nut is then tightened. Engine will be rotated to obtain all valve 
adjustments to manufacturer's specifications.  

CYLINDER HEAD OVERHAUL

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Engine Overhaul Procedures

  

CYLINDER HEAD DISASSEMBLY 

Mark valves for location. Using valve spring compressor, compress valve springs. Remove valve locks. 
Carefully release spring compressor. Remove retainer or rotator, valve spring, spring seat and valve. See Fig. 2 . 

Fig. 2: Exploded View of Valve Assemblies 

CYLINDER HEAD CLEANING & INSPECTION 

Clean cylinder head and valve components using approved cleaning methods. Inspect cylinder head for cracks, 
damage or warped gasket surface. Place straightedge across gasket surface. Determine clearance at center of 
straightedge. Measure across both diagonals, longitudinal center line and across cylinder head at several points. 
See Fig. 3 .  

On cast iron cylinder heads, if warpage exceeds .003" (.08 mm) in a 6" span, or .006" (.15 mm) over total 
length, cylinder head must be resurfaced. On most aluminum cylinder heads, if warpage exceeds .002" (.05 
mm) in any area, cylinder head must be resurfaced. Warpage specification may vary by manufacturer. If 
warpage exceeds specification on some cylinder heads, cylinder head must be replaced.  

Cylinder head thickness should be measured to determine amount of material which can be removed before 
replacement is required. Cylinder head thickness must not be less than the manufacturer's specification.  

If cylinder head required resurfacing, it may not align properly with intake manifold. On "V" type engines, 
misalignment is corrected by machining intake manifold surface that contacts cylinder head. Cylinder head may 
be machined on surface that contacts intake manifold. Using oil stone, remove burrs or scratches from all 
sealing surfaces.  

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Engine Overhaul Procedures