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Page 228
REPAIR INSTRUCTIONS
CHECKING RUNNING CLEARANCE
When using the Plastigage method of checking
running clearance, do not turn the crankshaft.
Doing so will destroy the Plastigage.
If checking the main bearing clearance with the
engine in the upright position (such as in the
chassis), the weight of the crankshaft must be
removed from the lower half of the bearing being
checked. To do this, place cardboard under the
crankshaft journal in the main caps adjacent to
the journal to be checked and tighten the
adjacent caps until the journal to be checked
seats against the upper bearing. Do not fully
torque screws. Capscrews on the bearing being
checked should be torqued to specification after
Plastigage strip has been positioned on the
bearing shell and the cap reinstalled. Support the
crankshaft at Nos. 1, 4 and 7 main journals, while
checking Nos. 2, 3, 5 and 6 bearings. Support the
crankshaft at the Nos. 3 and 5 journals, while
checking the Nos. 1, 4 and 7 bearings.
ENGINE OUT OF CHASSIS AND INVERTED
1. Use Plastigage to check the main bearing
clearance. Check each bearing, one at a
time, by placing a piece of Plastigage on the
journal and tightening the cap in place. The
bearing clearance is determined by
measuring the width of the crushed
Plastigage with the supplied gauge.
2. Place a section of Plastigage (2) on the
journal to be checked and assemble the
main bearing cap (1) to the cylinder block as
shown in Figure 238.
3. Apply a light coat of oil on the threads of the
bearing cap capscrews and secure the cap.
4. Tighten the capscrews to the specified
torque, 210 lb-ft (285 N•m), using torque
wrench J 24407, or equivalent. The
Plastigage strip will be crushed between the
bearing insert (3) and the crankshaft journal
(4).
238
Figure 238 — Checking Running Clearance with
Plastigage
5. Remove the capscrews and cap, and check
the bearing running clearance.
6. Check the width of the Plastigage using a
Plastigage width chart. After measuring
width, remove the Plastigage from the
bearing.
7. If the clearance is not within specification,
correct the clearance as required. Be sure to
use the proper size bearing(s).
r
If the clearance is less than specified,
check behind the bearing for dirt, chips
or burrs which would prevent the
bearing from seating properly.
r
If the bearing bores and inserts are
clean and undamaged, replace the
inserts with inserts sized to provide the
specified clearance.
1. Main Bearing Cap
2. Plastigage
3. Bearing Insert
4. Crankshaft Journal
5_106_00.bk Page 228 Friday, August 4, 2000 11:17 AM
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