h. Installation of Crankshaft and Main Bearings.
heating (fig. 3-136). If any of these defects are pres-
(1) If a new crankshaft is to be installed, steam
ent, the bearings must be replaced.
clean it to remove the rust preventive, blow out the oil
passages with compressed air and install the plugs.
Since the lower main bearing shells carry the
Then, install the crankshaft as follows:
crankshaft load, their condition will normally
indicate the need for replacement.
When a new or reground crankshaft is in-
Babbitt plated bearings may develop minute
stalled, new main and connecting rod (upper
cracks or isolated cavities. These are not
and lower) bearing shells and new thrust
detrimental to engine operation and are not
washers shall also be installed.
justification for bearing replacement.
(2) Install the upper grooved bearing shells in the
(21) Inspect the backs of the shells for bright
block. If the old bearing shells are to be used again, in-
spots which indicate they have been moving in the cap
stall them in the same locations from which they were
or cylinder block. If such spots are present, discard the
(3) Apply clean engine oil to all crankshaft jour-
(22) Measure the thickness of the shells at point C
nals and install the crankshaft in place so that the tim-
(fig. 3-137) with a micrometer and ball attachment as
ing marks on the crankshaft timing gear and the idler
illustrated in figure 3-138.
(23) The minimum thickness of a worn standard
(4) Install the upper halves of the crankshaft
main bearing shell is 0.123 inch. If any of the shells
thrust washers on each side of the rear main bearing
are thinner than this dimension, replace all shells.
support and the doweled lower halves on each side of
Table 3-3 lists the minimum bearing shell thickness
the rear main bearing cap. The grooved side of the
for a new standard and undersize bearings, and the
thrust washers must face toward the crankshaft thrust
crankshaft main bearing journal diameters corre-
surfaces (fig. 3-131).
sponding to each bearing size.
Table 3-3. Main Bearing Shell Dimensional Data
If the crankshaft thrust surfaces were re-
ground, it may be necessary to install over-
Minimum new bearing
size thrust washers on one or both sides of the
Bearing journal dia.
rear main journal. Refer to figure 3-135, D
and table 3-4.
Table 3-4. Thrust Washer Dimensions
Dimension of reground crankshaft
(24) Measure the clearance between main bear-
ings and crankshaft journals. If the crankshaft is in
(5) Install the lower bearing shells (no oil grooves)
place, measure the clearance with a soft plastic meas-
in the bearing caps, If the old bearing shells are to be
uring strip forced between the journal and bearing. If
used again, install them in the same bearing caps from
the clearance is, or exceeds 0.006 inch, replace all bear-
which they were removed. Lubricate the bolt threads
ing shells. With new shells, the clearance should be
and bolt head contact surfaces with a small quantity of
0.0010 to 0.0040 inch.
International Compound No. 2, or equivalent. Draw
(25) If the crankshaft is removed, install the bear-
the bolts up snug (fig. 3-129). Then, rap the caps
ing shells in the block. Replace bearing caps and
sharply with a soft hammer to seat them properly.
torque bearing cap bolts to 120-130 lb-ft. Measure in-
(6) Draw the bearing cap bolts uniformly tight,
side diameter of bearings and compare with crank-
starting with the center cap and working alternately
shaft main bearing journal diameters as listed in table
toward both ends of the block, to 120-130 lb-ft torque.
3-3. The tolerances specified in (24) above apply.
Rotate the crankshaft to make sure that it rotates free-
(1) Install plugs in crankshaft, if removed.
(2) Install the oil pump drive gear on the crank-
If the bearings have been installed properly,
shaft (fig. 3-99).
the crankshaft will turn freely with all of the
(3) Position timing gear key (17, fig. 3-130) in
main bearing cap bolts drawn to the specified
keyway of crankshaft and drive the timing gear (18) on
the crankshaft as shown in figure 3-139.