1.3.4
Main Bearings
DETROIT DIESEL 53
crankshaft. See Section 1.3 under Crankshaft Inspec-
tion for removal of ridges and inspect& of the
crankshaft.
Do not replace one main bearing shell alone. If one
bearing shell requires replacement, install both new
upper and lower bearing shells. Also, if a new or
reground crankshaft is to be used, install all new
bearing shells.
Bearing shells are available in .010", ,020" and
.030" undersize for service with reground crankshafts.
To determine the size bearings required, refer to
Crankshaft Grinding in Section 1.3.
Bearings which are .002" undersize are available to
compensate for slight journal wear where it is
unnecessary to regrind the crankshaft.
NOTE: Bearing shells are NOT reworkable from
one undersize to another under any
circumstances.
Inspect the crankshaft thrust washers. If the washers
are scored or worn excessively or the crankshaft end
play is excessive, they must be replaced. Improper
clutch adjustment can contribute to excessive wear on
the thrust washers. Inspect the crankshaft thrust
surfaces. Refer to Install Crankshaft in Section 1.3. If.
Fig. 9- Crankshaft Thrust Washers in Place
after dressing or regrinding the thrust surfaces, new
standard size thrust washers do not hold the
end of the connecting rods will be blocked off. Used
crankshaft end play within the specified limits, it may
bearing shells must be reinstalled on the same journal
be necessary to install oversize thrust washers on one
from which they were removed.
or both sides of the rear main bearing. A new
standard size thrust washer is .1190" to .1220" thick.
1. When installing an upper main bearing shell with
Thrust washers are available in ,005" and
the crankshaft in place. start the plain end of the
.010" oversize.
bearing shell around the crankshaft journal so that.
when the hearing is in place. the tang will lit into the
groove in the bearing support.
Install Main gearing Shells ( Crankshaft in
Place)
2. Install the lower main bearing shell so that the tang
on the bearing tits into the groove in the bearing cap.
Make sure all of the parts are (clean. Then apply clean
engine oil to each crankshaft journal and install the
3. Assemble the crankshaft thrust washers (Fig. 9)
upper main bearing shells by reversing the sequence
before installing the rear main bearing cap. Clean
of operations given for removal.
both halves of each thrust washer carefully and
remove any burrs from the washer seats -- the slightest
burr or particle of dirt may decrease the clearance
between the washers and the crankshaft beyond the
specified limit. Slide the upper halves of the thrust
washers into place. Then assemble the lower halves
over the dowel pins in the bearing cap.
The upper and lower main bearing shells are not
NOTE: The main hearing caps are bored in
alike; the upper shell is grooved and drilled for
position and marked 1 2. 3. etc. They must be
lubrication -- the lower shell is not. Be sure to install
installed in their original positions with the
the grooved and drilled bearing shells in the cylinder
marked side of each cup facing the same side
block and the plain bearing shells in the bearing caps,
of the cvlinder block that carries the engine
otherwise the oil flow to the bearings and to the upper
serial number.
SEC. 1.3.4 Page 5
April. 1974
