DETROIT DIESEL 53
b. Measure the bearing bores. The bearing bores
must be 3.751 " to 3.752 " (V-type block). If the
bores do not fall within these limits, discard the
2. Check the block bores as follows:
c. Check the main bearing bores for alignment.
a. Make sure the seal ring grooves
The bearing bores may be considered properly
thoroughly clean. Then inspect the grooves and
aligned with one another if the crankshaft can
lands for evidence of pitting and erosion. Two
be rotated freely by hand, after new main
grooves are provided above the air inlet ports of
bearing shells have been installed and
each cylinder bore in the block.
lubricated and the bearing caps have been
secured as in Step 3a.
However, a cylinder liner seal ring is required in
d. Finished and unfinished service replacement
the upper groove only. The lower groove
main bearing caps are available. However,
is provided for the seal ring if inspection reveals
when using the finished replacement caps, it
extensive pitting or erosion along the upper land
may be necessary to try several caps in each
or inner surface of the upper groove. If both
location required before the proper fit is
grooves are eroded to the extent that sealing is
obtained. When using the unfinished main
affected, then the block must be replaced.
bearing caps, install the caps in the cylinder
block as in Step 3a. Then, with the caps in
b. Measure the entire bore of each cylinder with
place, line-bore the main bearing caps to the
cylinder bore gage J 5347 (Fig.6.) which has a
finished main bearing bore dimensions specified
dial indicator calibrated in .0001 " increments.
in Step 3b. If a replacement bearing cap is
Use dial bore gage setting tool J 23059 to preset
installed, be sure to stamp the correct bearing
the cylinder bore gage to zero. Measure each
number on the new cap.
block bore at the positions indicated in Fig.7., on
axis 90 ' apart. If the diameter does not exceed
4.5235 " at position "A", 4.4900 " at position "B"
NOTE: Use the unfinished caps in the front and
(and a sealing problem hasn't occured), or
intermediate journal positions only.
4.3595 " at position "C" and "D", then the block
may be reused. Also, the taper and out of round
4. Make sure the cylinder liner counterbores in the
must not exceed .0015 ".
block are clean and free of dirt. Then check the depth.
3. Check the main bearing bores as follows:
The depth must be from .300 " to .302 " and must not
a. Lubricate the threads and the underside of each
vary more than .0015 " throughout the entire
bolt head with a small quantity of International
circumference. The counterbored surfaces must be
Compound No. 2, or equivalent. Install the
smooth and square with the cylinder bore within .001 "
bearing caps and tighten the bolts to the
total indicator reading. There must not be over .001 "
difference between any two adjacent cylinder
counterbores, when measured along the cylinder
IMPORTANT: It is imperative that the main
longitudinal centerline of the cylinder block.
bearing caps are reinstalled in their original
5. Check all of the machined surfaces and threaded
positions to maintain the main bearing bore
holes in the block. Remove nicks and burrs from the
alignment. The bearing caps are numbered to
machined surfaces with a file. Clean-up damaged
correspond with their respective positions in the
threads in the tapped holes with a tap or install helical
block. The number of the front bearing cap is also
stamped on the face of the oil pan mounting
flange of the block, adjacent to its permanent
6. Replace loose or damaged dowel pins.
location in the engine as established at the time of
manufacture. The No. I cylinder and main
7. Install all required plugs. Use a good grade of
bearing cap is always located at the end opposite
sealing compound on the threads of the plugs. If a new
the flywheel end of the block (Fig. 8).
service block is used, make sure the top surface is
plugged correctly to prevent low oil pressure or the
NOTE: Main bearing cap bolts are especially
accumulation of abnormal quantities of-oil in the
designed for this purpose and must not be
replaced by ordinary bolts.
8. If a new service replacement block is used, stamp
the engine serial number and model number on the top
1972 General Motors Corp.