Hummer H1 (2002+). Manual - part 25

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Engine 2-61

05745159

NOTE: Be sure to inspect the piston cooling oil tubes in turbo
diesel blocks. Verify that the tubes are clear (Figure 2-101).

Figure 2-100: Camshaft Bearing Locations

Figure 2-101: Piston Oil Cooling Feed and Spray

Orifice Locations

Inspection

Check all of the block surfaces for nicks, scratches, cracks,
damaged threads, or evidence of porosity at any point. Minor
nicks and scratches can be smoothed with a fine tooth file or
180 grit emery. Damaged threads can be either chased, or re-
paired with Helicoil stainless steel thread inserts. Replace the
block if cracked, or if porous spots are evident.

Light discoloration of gasket surfaces and cylinder bores is
normal and not a cause for replacement. However, evidence of
severe overheating and heat checking will require closer atten-
tion to dimensional checks.

Check condition of the expansion plugs (Figure 2-102), and
camshaft plug. Replace the plugs if corroded, rusted, loose, or
coolant leakage is evident. Refer to the procedure in this sec-
tion if plug replacement is required.

Figure 2-102: Cylinder Block Expansion Plug

Locations

Check the cam bearings. Locations in the block are shown
(Figure 2-100).

It is not necessary to replace the bearings if they only have a
burnished, or polished appearance, and wear is very minimal.
However, replace all of the bearings if one or more are scored,
flaking, distorted, etched, pitted, loose, or misaligned. Also re-
place the bearings if the block was hot tank cleaned with the
bearings in place. Refer to the bearing replacement procedure
in this section.

On turbocharged engines, check the oil feed holes at the rear of
the block near the oil pump drive. Make sure the feed holes are
clear and not plugged. This is important as any restrictions will
result in turbocharger failure.

Remove and inspect the oil pressure regulator and safety
valves. Replace the regulator valve plug; do not reuse it. Re-
place the two valves if seized, binding, or plugged. Do not try
to salvage the valves.

CAM BEARING AND

BORE LOCATIONS

FEED

ORIFICE

OIL SPRAY TUBES

FEED

ORIFICE

EXPANSION PLUGS

SMALL EXPANSION PLUG

PIPE PLUG

2-62

Engine

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Check the pipe plugs at the sides and front of the block
(Figure 2-103). Replace any plugs that are loose or leaking.
Coat replacement plug threads with Permatex #2, or high temp
silicone sealant before installation.

Figure 2-103: Cylinder Block Valve and Plug

Locations

Cylinder Bore and Piston Measurement

Check surface flatness of the cylinder block deck with a
straightedge and feeler gauge (Figure 2-104). Deck surface
flatness must not vary by more than 0.002 in. (0.05 mm) in any
six inch (15 cm) length, or 0.006 in. (0.15 mm) overall. Re-
place the cylinder block if deck flatness is not within stated
limits. Do not attempt to salvage a block by machining the
deck surface. This practice will result in valve-to-piston con-
tact.

Figure 2-104: Checking Deck Flatness

Check condition of the cylinder head and front cover dowel
pins (Figure 2-104). Remove and replace any pins that are
loose.

Inspect the main bearing saddles, bearing caps, front cover sur-
face, block webs, and pan rails (Figure 2-105). Replace the
block if cracks, severe scoring, or distortion is evident at any
point.

Measure degree of wear and taper in each cylinder bore with
bore gauge J–8087 (Figure 2-106).

Refer to the Service Piston and Cylinder Bore Specifi-
cations data at the end of this section for bore dimen-
sions.

Center the bore gauge in the cylinder and zero the dial
indicator (Figure 2-106).

Work the gauge slowly up and down the cylinder
from top to bottom. Take measurements at cylinder
axis points “A” and “B” (Figure 2-107). Note that
most wear occurs in the top 2 1/2 in. (63.5 mm) of the
cylinder.

Figure 2-105: Rail, Web, Bearing Inspection Points

NOTE: Cylinder number 7 and 8 require an additional 0.0005
in. (0.013 mm) for piston clearance. Take this into account
when checking bore wear.

Maximum allowable service wear and taper is 0.005
in. (0.013 mm).

Rebore the cylinder and replace the pistons if wear
and taper exceed allowable service limits.

NOTE: Replace the cylinder block if bore diameter exceeds
4.075 in. (103.521 mm) on cylinder 1-6 and 4.076 in. (103.534
mm) on cylinders 7 and 8.

PIPE

PLUGS

OIL

SAFETY

VALVE

OIL PRESSURE

REGULATOR VALVE

PLUG

BLOCK PLUG

DOWEL PIN

CYLINDER BLOCK DECK

DOWEL PIN

STRAIGHTEDGE

BEARING CAP

CAMSHAFT

THRUST PLATE

SURFACE

BEARING

SADDLES

FRONT COVER

SURFACES

WEB

PAN RAIL

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Engine 2-63

05745159

Figure 2-106: Measuring Cylinder Taper and Wear

with Bore Gauge

Measure piston skirt diameter at the centerline of the piston pin
but at a right angle (opposite) to the pin. Refer to the “Service
Piston and Cylinder Bore Specifications” data at the end of this
section for dimensions.

Remove the piston rings, insert the piston in the bore, and
check piston-to-bore clearance with a feeler gauge. Clearance
should not exceed 0.004 in. (0.120 mm) on cylinders 1 through
6, and 0.005 in. (0.133 mm) on cylinders 7 and 8.

•

Replace the piston if the skirt is severely scored,
collapsed, or worn below specified limits.

•

Reuse the piston if in good condition and wear is
minimal. However, if the cylinder bore is worn and
requires reboring, the piston must be replaced, even
if it’s in good condition.

•

Replace the piston if the bore is OK but piston-to-
bore clearance is greater than specified.

Remove all the expansion/freeze plugs with a punch and ham-
mer. Coat the edges of replacement plugs with Permatex #2, or
a high temp RTV sealer. Seat the new plugs in the block with a
suitable size socket and hammer. Be very sure each plug is
firmly seated. Replace any plug that becomes distorted during
installation; do not salvage it.

Figure 2-107: Cylinder Bore Measuring Points

BORE GAUGE

–

8087

CYLINDER BORE

AXIS “A”

AXIS “B”

2-64

Engine

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Cylinder Boring and Honing Information

Check the ID letters stamped on the cylinder block pan rails.
These letters identify the production standard piston grade size
and cylinder bore. The letters used are J, K, G, and T. Grade
and sizes are listed in the service piston and bore chart at the
end of this section. Use this information as a check - before -
ordering parts or performing any machining operations.
Production and oversize pistons from the factory are all the
same weight, therefore engine balance is not affected. This
means that a low mileage block does not have to have all the
cylinders rebored if only one or two require this. However, on
high mileage blocks, it is better to rebore all the cylinders to
maintain equal cylinder pressures.
The main bearing caps should be installed and tightened to spec-
ified torque before commencing boring operations. The block
decks should also be clean, smooth, and free of nicks and burrs.
The boring bar must rest on a flat, even surface to avoid an off-
center bore. Boring and honing plates are also recommended.
Keep boring bar cutting tool speed and feed rates within the
tool manufacturers recommendations. Excessive feed or speed
rates can produce unwanted tool marks. Extra honing opera-
tions will be required to correct this.
Boring should be a two step operation consisting of: a rough
bore to remove about 90% of the required stock, and a finish
bore to within 0.003-0.005 in. (0.0762-0.1270 mm) of the de-
sired final size. The final bore size, including required piston-
to-bore clearance, will be achieved during honing operations.
Cylinder honing is required to break the glaze, or to achieve fi-
nal surface finish and piston clearance after boring operations.
Glaze breaking hones are designed for hand operation in a drill
motor. This type of honing only requires breaking through the
varnish buildup on the walls. Machine operated cylinder hones,
such as those built by the Sunnen Corp., are required for
achieving final finish and size.
Honing operations on rebored cylinders should also be a two
step procedure. A rough hone to within 0.0005 in. (0.13 mm)
followed by a finish hone to size. The rough honing establishes
size while finish honing generates the required 45° cross-hatch
pattern. The crosshatch pattern provides a surface that will retain
oil for proper wall lubrication. Perfectly smooth finishes are to
be avoided.

NOTE: Service oversize pistons are available in one size only
which is 0.020 in. (0.50 mm) over. This is the maximum allow-
able cylinder oversize. Note this before initiating boring operations.

Figure 2-108: Measuring Piston Skirt Diameter

CAMSHAFT BEARING REPLACEMENT

Camshaft bearing tool set J–33049 plus adapters J–6098-11
and J–6098-12 and tool set J–6098-01 are required for bearing
replacement.
During removal, bearings 1 and 5 are removed last because
they must be in place to support the pilot tool. For this reason,
these bearings must be installed first during replacement.
The front (no. 1) bearing has two oil feed holes. The remaining
bearings have a single oil feed hole. All of the bearing feed
holes must be aligned with the oil feed holes in the bearing
bores.
Cam bearings 1, 2, 3, and 4 are the same size. However, bear-
ing number 5 is a different diameter. Be sure the correct bear-
ing is installed in each bore. Replacement bearings are
numbered to help avoid incorrect placement.
The front (no. 1) bearing has a notch in it. This notch must face
out toward the block front. Each of the bearings also has an oil
groove. Install the bearings so the groove is at the top of the
bore toward the upper part of the block.

Bearing Replacement Procedure

Remove camshaft plug at rear of block (Figure 2-109).
Use long wood dowel or pipe tool and hammer to tap plug
out rear of block. Discard plug afterward. It is not reus-
able.

Remove No. 2 bearing as follows:

Insert pilot from tool set J–33049 in No. 1 bearing
(Figure 2-109).

Slide puller screw from tool set J–33049 through pilot
and through No. 2 bearing.

Install adapter J–6098-11 on puller screw and seat
adapter in No. 2 bearing.

Tighten nut on puller screw to remove bearing.

Remove bearings 3 and 4 as described in step 2.

Remove bearing No. 5 with driver handle from tool set
J–6098-01 and adapter J–6098-12 (Figure 2-110).

Remove bearing No. 1 with driver handle and J–33049
(Figure 2-110).

Figure 2-109: Removing Cam Bearings 2, 3, and 4

PISTON SKIRT

MICROMETER

ADAPTER J–6098-11

PILOT FROM

PULLER SCREW

NO. 2

NO. 3

NO. 4

J–33049

FROM J–33049

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