Hummer H1 Service Manual page 103

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2-66 Engine
CRANKSHAFT SERVICE
Clean the crankshaft with solvent and clear the journal oil
holes with a wire brush if necessary. Dry the crankshaft with
compressed air or lint free shop towels.
Inspect condition of rod and main journals (Figure 2-113). The
journals must be smooth and free from scoring, grooves, taper,
cracks, and checking/galling.
Minor nicks and burrs can be removed with an oil stone and
380 grit emery. Minor scratches, or scoring on journal surfaces
can be smoothed with 320 grit emery followed by polishing
with crocus cloth.
Check for cracks on all surfaces including the counterweights.
Also check the threads in the crankshaft flange and nose.
Rusty, rough threads can be cleaned up with a tap. However,
replace the shaft if the threads are seriously damaged.
Magnaflux or Zyglo the crankshaft if cracks are suspected.
Although the crankshaft journals can be machine polished to
restore surface finish, replace the crankshaft if damaged, dis-
torted, worn, or scored. Do not attempt to salvage it.
COUNTERWEIGHT
NOSE
ROD JOURNAL
Figure 2-113: Crankshaft Inspection Points
Checking Crankshaft Journal Diameter and
Runout
There are three main journal diameter ranges. These ranges are
identified by a color code paint mark near one of the journals.
The three size range color codes are blue, orange/red, and
white. Note the code on the crankshaft and refer to the specifi-
cation charts at the end of this section for size ranges.
Use a micrometer to check journal diameter. Measure both
ends of each journal to check for taper along with wear
(Figure 2-114).
Journal wear or taper must not exceed 0.0002-0.001 in. (0.05-
0.025 mm).
Mount the crankshaft in a holding fixture and check runout at
center (#3) main bearing journal (Figure 2-115).
SEAL SURFACE
MAIN JOURNAL
OIL HOLES
Crankshaft runout should not exceed 0.0002 - 0.0008 in. (0.005
- 0.020 mm). Replace the crankshaft if runout is greater than
specified. Do not attempt to straighten a cast iron crankshaft.
Figure 2-114: Measuring Journal Diameter
CENTER
MAIN JOURNAL
HOLDING FIXTURE
DIAL INDICATOR
Figure 2-115: Measuring Crankshaft Runout
MICROMETER
J–8001
®