To avoid damage to the upper main bearing shells during Installation, the services of two
technicians will be required. Be sure the bearing shells are not Interchanged. The upper main
bearing shell has a drilled hole to allow passage of lubricating oil, and must be Installed in the
cylinder block If the lower, undrilled bearing shell is installed in the block, severe crankshaft
damage will result.
Lightly lubricate the crankshaft journal with a small amount of lubricating oil, MIL-L-2104, position the upper main
bearing shell (22 or 23) against the crankshaft (32) with the tang of the bearing opposite the tang recess in the
cylinder block (58).
Have an assistant slowly rotate the crankshaft (32) counterclockwise (when viewed from the front of engine)
while maintaining upward, rotational pressure on the bearing shell (22 or 23).
Work the bearing shell (22 or 23) around the crankshaft (32) by hand while the crankshaft is being turned.
As the bearing shell (22 or 23) approaches its final position, make sure the tang is aligned with the tang slot in
the cylinder block (58). If necessary, have the assistant rock the crankshaft back-and-forth while applying side
pressure on the bearing shell to align the slot and tang.
If the bearing shell (22 or 23) cannot be completely installed using steps (9), (10), and (11), above, use the
removal tool (Figure 9-33) to install the shell as follows:
Work the main bearing shell (22 or 23, Figure 9-24) around the crankshaft (32) at least 135 degrees. Not
more than 2.5 inches (63.5 mm) of the bearing shell should protrude, and the tang must be exactly aligned
with the slot.
Install the removal tool (Figure 9-33) in the crankshaft (32), and have the assistant rotate the crankshaft
slowly while holding the installation tool in place. Be extremely careful that the tang and slot remain in
alignment as the bearing shell is brought to its final position.
If removed, install the dowel (21) in the main bearing cap (18).
Before Installing the lower bearing shell in the cap, be sure all traces of dirt or foreign material
Is removed from both cap and bearing shell. Even a small amount of foreign matter trapped
between the bearing and cap will decrease bearing shell-to-journal clearance and will result in
premature wear or burned bearings shells.
Install the bearing shell (19 or 20) in the main bearing cap (18). Be sure the bearing is firmly seated in the cap.
Do not lubricate the bearing shell at this time.
To avoid a false clearance measurement and subsequent engine damage, the following
procedure is necessary when using Plastigage to check bearing shell clearance.
Rotate the crankshaft so that the counterweight next to the main bearing shell being checked is facing down.
Using a small hydraulic jack, under the counterweight, support the crankshaft (32) so that it is seated firmly
against the upper bearing shell (22 or 23).