Hummer H1 Service Manual page 101

_____________________________________________________________________
2-64 Engine
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
1.
2.
3.
4.
5.
PISTON SKIRT
MICROMETER
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:
a. Insert pilot from tool set J–33049 in No. 1 bearing
(Figure 2-109).
b. Slide puller screw from tool set J–33049 through pilot
and through No. 2 bearing.
c. Install adapter J–6098-11 on puller screw and seat
adapter in No. 2 bearing.
d. 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).
NO. 4
NO. 3
NO. 2
PULLER SCREW
FROM J–33049
Figure 2-109: Removing Cam Bearings 2, 3, and 4
ADAPTER J–6098-11
PILOT FROM
J–33049
®