Content .. 26 27 28 29 ..

Hummer H1 (2002+). Manual - part 28

____________________________________________________________________

Engine 2-73

05745159

Figure 2-134: Intake and Exhaust Valve Components

Figure 2-135: Pre-combustion Chamber Removal

Figure 2-136: Cover Removal/Installation

Cleaning and Inspection

Clean the cylinder heads and valve components in parts clean-
ing solvent. Use carb cleaner and a wire brush to remove stub-
born carbon deposits on the heads valves and prechambers.

Check flatness of intake/exhaust manifold seating surfaces
with straightedge. Surfaces must be flat to within 0.006 in.
(0.15 mm).

Check cylinder head flatness with straightedge and feeler
gauge (Figure 2-137). Overall (end-to-end) flatness should not
vary by more than 0.006 in. (0.152 mm). Replace the head if
warped or distorted. Do not machine the head.

Figure 2-137: Checking Cylinder Head Flatness

Inspect the combustion prechambers (Figure 2-138). Minor
cracks under 3/16 in. (0.48 mm) in length are not cause for re-
placement. Install new chambers only when cracks extend be-
yond the indicated length (Figure 2-138).

INTAKE VALVE

VALVE STEM SEAL

SHIM

VALVE SPRING AND

DAMPER ASSEMBLY

SHIELD

RETAINER

LOCKS

RETAINER/ROTATOR

SHIELD

VALVE SPRING AND

DAMPER ASSEMBLY

SHIM

VALVE STEM SEAL

VALVE STEM AND

GUIDE SEAL

EXHAUST VALVE

PRE-COMBUSTION CHAMBER

CYLINDER HEAD

GASKET

COVER

STRAIGHT EDGE

FEELER

GAUGE

2-74

Engine

_____________________________________________________________________

Figure 2-138: Prechamber Inspection Points

Check fit of each pre-chamber in the cylinder head. Replace
loose (or cracked) chambers. Oversize chambers are available
when needed. The oversize parts are marked with ID code
“08.” The code numerals appear on the chamber crown, side,
or interior (Figure 2-139)

Figure 2-139: Oversize Prechamber I.D.

Measure valve stem clearance with a dial indicator. Required
clearance is 0.001-0.003 in. (0.026-0.069 mm) for intake and
exhaust valves. If clearance is beyond limits, ream the valve
guide with reamer (Figure 2-140) and install new valve with
0.0035 in. (0.089 mm) larger stem.

Figure 2-140: Typical Method of Reaming

Valve Guides

Check the valve stems for wear, scoring, or distortion. Inspect
the faces for pitting, cracks, or burnt segments. Also inspect
the lock grooves at the stem top. Be sure the grooves are free of
cracks, worn or broken lands, or chipped spots. Replace any
valve exhibiting the foregoing conditions.

Grind the valve faces only lightly to obtain the required 45°
face angle (Figure 2-141). Take care to avoid cutting into the
valve margin. Quik Way, Van Norman, Sioux or similar qual-
ity equipment is recommended.

Figure 2-141: Valve Refacing Angles and Widths

Grind the valve seats to the required 46° angle with the previ-
ously recommended equipment. Or, use a 4-6 blade carbide
cutter to dress the seat.

Lightly lap the valves and seats with a fine grit compound.
Clean the valves and seats and inspect the lap marks. The lap
marks, which represent the actual contact areas on the valves
and seats, should be concentric, and equal in width throughout.
Ideal seat width is 0.063 in. (1.6 mm).

If the lap marks are thick-thin or eccentric, the valves or guides
are worn beyond tolerance. Verify by rechecking valve stem
clearance and valve seat runout with a dial indicator.

S02-240

ACCEPTABLE

CRACK LENGTH

NOT OVER

3/16” IN (5 MM)

UNACCEPTABLE

CRACK LENGTH

OVER 3/16” (5 MM)

A. HEAD GASKET

SEALING BEAD MARK

B. FIRE SLOT

SIZE CODE

LOCATIONS

REAMER

REAMER
HANDLE

J–5830-1

90°

A-SEAT WIDTH = INTAKE 0.035-0.060 in. (0.089-1.524 mm)

EXHAUST (0.060-0.093 in. (1.524-2.36 mm)

B-FACE ANGLE (INTAKE & EXHAUST) = 45°

C-SEAT ANGLE (INTAKE & EXHAUST) = 46°

D-VALVE FACE CONTACT AREA

____________________________________________________________________

Engine 2-75

05745159

Cylinder Head Reassembly

Scuff sand all gasket surfaces with 180 grit paper.

Clean the valvetrain parts and cylinder head with solvent
and dry with compressed air.

Install new freeze plugs in heads if necessary. Apply
Permatex #2 or high temp adhesive/sealer to edges of
plugs before installation. Be sure plugs are properly
seated.

Install combustion prechambers in cylinder heads
(Figure 2-142). Chambers should be flush to no more than
0.002 in. (0.05 mm) above head surface.

Install new nylon stem and guide seals on exhaust valve
guides.

Lubricate valve stems and guides with 30w engine oil, or
assembly lube.

Install valves as follows (Figure 2-142):

Insert valve into guide and through nylon seal on
exhaust valves.

Install shim.

Lubricate and install stem seal on valve.

Position valve spring and damper on shim.

Install shield followed by retainer on valve spring.

Compress spring with spring compressor tool
(Figure 2-133).

Install valve locks. Be sure locks are fully seated be-
fore proceeding. Use petroleum jelly to hold locks in
place during installation.

Release and remove compressor tool.

Check valve spring installed height:

Use dividers and micrometer or vernier caliper
(Figure 2-143).

Measure height from bottom of spring to top of shield
as shown.

Correct height is 46 mm (1.81 in.). Height can exceed
specified figure by 0.127 mm (0.005 in.) but must
never be lower than specified.

Use thicker shim to decrease height, or thinner shim
to increase height Replace any valve spring that can-
not be set to specified height.

Apply Permatex #2, or high temp sealant to threads of
coolant temperature sender. Then install the switch in the
left head (Figures 2-132 ).

10. Install access cover and gasket, if removed. Use Permatex

#2 or high temp sealant on gasket.

11. Cover assembled heads if they will not be installed

immediately.

Figure 2-142: Valvetrain Installation Sequence

Figure 2-143: Installed Height of Valve Spring

INTAKE

VALVE

EXHAUST

VALVE

SHIM

SPRING AND

DAMPER

SHIELD

STEM

SEAL

RETAINER/

ROTATOR

LOCKS (2)

RETAINER

DESIRED

SPRING HEIGHT IS

1.81 in. (46 mm)

SHIM

SHIELD

2-76

Engine

_____________________________________________________________________

LIFTER, PUSHROD, ROCKER ARM SERVICE

Clean the rocker arms, shafts, pushrods, guides, clamps, and
lifters in parts cleaning solvent.

Immerse the lifters in solvent and use a pushrod to stroke the
lifter plunger. Replace any lifter that is collapsed, or if fluid
cannot be pumped out oil hole when plunger is stroked.

Inspect the lifter roller and bearings. Replace any lifter that ex-
hibits wear on the body, roller, or bearings. Turn the roller and
note action. Replace the lifter if the roller binds, or is seized.

Check each pushrod (Figure 2-144) for distortion and wear.
Replace any pushrod that is bent. Check the pushrod ball ends.
Replace the pushrod if either ball end is flattened, scored, or
loose.

Inspect the lifter guide plates and clamps (Figure 2-144). Re-
place the plates and clamps if worn, or distorted. Also make
sure the guide plates are a proper slip fit on the lifters.

Inspect the rocker arms and shafts for wear, cracks, scoring/
grooving, or distortion. Check the pushrod contact area on each
arm for wear, or scoring. Replace the rocker arms, or shaft as
needed.

Discard the rocker arm retainers (Figure 2-145). Also discard
the rocker shaft retainers if bent, distorted, or cracked.

Figure 2-144: Lifter and Pushrod Components

Figure 2-145: Rocker Arm and Shaft Components

DAMPER AND FLYWHEEL SERVICE

The flywheel can be immersed in cleaning solvent. However,
the torsional damper should only be wiped clean with a cloth
wetted with parts cleaner. The damper has a rubber composite
insulator (Figure 2-146). This insulator can be damaged by im-
mersion in some cleaning solutions.

Inspect the damper insulator ring (Figure 2-146). Replace the
damper if the ring is cracked, distorted, protruding, or loose
(hub can be turned independently of outer shell). Also check
the hub bore, keyway, and seal surface. Minor nicks or
scratches can be smoothed with 320 grit emery but replace the
damper if these surfaces are severely scored, or cracked. Clean
the bolt hole threads with a tap if necessary.

CAUTION:

6.5L diesel engines are externally balanced. The

torsional damper is an integral part of the balancing mecha-
nism. Never use a solid, or similar non-recommended damper
as this practice can result in a broken crankshaft. Use factory
replacement dampers only.

Inspect the flywheel carefully (Figure 2-147). Look for worn,
chipped, or broken ring gear teeth and check the hub for cracks
at the mounting bolt holes. Place the flywheel on a flat surface
and check the body for warping, distortion, or cracks at the
converter attaching bolt holes. Replace the flywheel if it exhib-
its any of the foregoing conditions.

NOTE:

The ring gear is not serviced separately. It is only

available as part of a new flywheel.

GUIDE CLAMP

GUIDE PLATE

PUSHROD

ROLLER LIFTER

ROCKER ARMS

ROCKER ARM SHAFT

ROCKER SHAFT

RETAINER AND BOLT

ROCKER ARM

RETAINER

Content .. 26 27 28 29 ..