TM 5-3810-300-24&P-3
1.1
Cylinder Block
bearing cap is always located at the end opposite
to 155-185 Ib-ft (211-251 Nm) torque). If a main
the flywheel end of the cylinder block Fig. 18),
bearing bore is more than .001 " out of alignment,
regardless of engine rotation or accessory
the block must be line-bored or scrapped.
arrangement. As originally manufactured, the main
Misalignment may be caused by a broken
bearing caps are installed with the numbered side
crankshaft, excessive heat or other damage.
facing the blower side of the engine. Machining of
d.
If the main bearing bores are not in alignment or a
the cylinder block and main bearing caps is such
replacement bearing cap is used, the block must be
that the mating parts are "offset" to prevent
line-bored. Install the bearing caps in their original
installation of the bearing caps 180 from their
positions and tighten the bolts to 165-175 lb-ft (244-
correct position. However, if an engine has been
238 Nm) torque (or tighten the nuts, if used, to 140-
converted for a new application and the cylinder and
155 lb-ft (190-211 Nm) torque). Line- bore the
bearing numbering sequence has been reversed,
block, but do not remove more than .001 " stock.
the bearing caps must be reinstalled in the original
After boring, all bores must be within the specified
positions regardless if the block and bearing caps
limits of 3.812 " to 3.813 "
have or have not been re-numbered.
8. Refer to the Cylinder Block Plugging Charts shown
b.
Finished and unfinished main bearing caps are
at the end of this manual and install the necessary plugs
available for replacing broken or damaged caps.
and dowels.
When fitting a finished replacement bearing cap, it
9. Replace loose or damaged dowel pins. The dowels
may be necessary to try several caps before one
at the ends of the cylinder block must extend 5/8" from
will be found to provide the correct bore diameter
the face of the block.
and bore alignment. If a replacement bearing cap
The dowels used to retain the crankshaft thrust washers
is installed, be sure to stamp the correct bearing
on the rear main bearing cap must extend .110" to .120"
position number on the cap.
from the surface of the bearing cap.
NOTE: Use the unfinished bearing caps for the front
NOTE: When required, an oversize rear main
and intermediate bearing positions. The finished
bearing cap dowel pin is available.
bearing caps, machined for the crankshaft thrust
washers, are to be used in the rear bearing position.
10. Replace main bearing cap studs, if used, which are
damaged or broken. Install new studs to a height of 4" +
c.
Main bearing bores are line-bored with the bearing
1/32" above the upper bearing seat at a torque of 35-75
caps in place and thus are in longitudinal alignment.
Ib-ft (47-102 Nm).
Bearing bores may be considered properly aligned
with one another if the crankshaft can be rotated
11. If used, replace damaged or broken cylinder head
freely by hand after new bearing shells have been
studs. Install and drive a new stud to a height of 4-3/8" +
installed and lubricated and the bearing caps have
1/32" at a minimum torque of 75 lb-ft (102 Nm) torque.
been secured in place and the bolts tightened to
180-190 lb-ft (224-258 Nm) torque (or nuts
12. Examine the tapped bolt holes for the cylinder head
tightened
or main bearing cap bolts and, if the threads are
damaged, "clean-up" the threads or install a helical
thread insert. The tapped holes may be tapped with a
5/8"-11 UNC3B tap. All cylinder head bolt or stud holes
must have the threads extending 1.84" below the block
surface.
NOTE: The current service replacement cylinder
blocks use a special cylinder head bolt in all
positions.
13. Check the drive pins (which plug the vertical oil
Fig. 18-Cylinder Block Markings
galleries) in the corners of the block to be sure they are
flush with or below the top surface of the block.
14. Check the remaining cylinder block surfaces and
threaded holes. Check all of the mating surfaces, or
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