The hex head of the crankshaft bolt may
be used to bar or turn the crankshaft.
However, t h e b a r r i n g o p e r a t i o n s h o u l d
ALWAYS be performed in a clockwise di-
rection.
It is very important to make
certain that the bolt has not been loos-
ened during the barring operation.
O t h e r w i s e serious engine damage may re-
sult i f t h e v i b r a t i o n d a m p e r i s n o t
securely fastened to the crankshaft.
CRANKSHAFT MAIN BEARINGS
Description
bearing shells
The crankshaft main
(Figure 11B-86) are precision made and
are replaceable without machining. They
Figure 11B-85. Crankshaft Cap
consist of an upper bearing shell seated
Mounting
in each cylinder block main bearing sup-
port and a lower bearing shell seated in
1. Tighten the bolt to 180 lb-ft (244 Nm)
The bearing
each main bearing cap.
torque.
shells are prevented from endwise or ra-
dial movement by a tang at the parting
2. Strike the end of the bolt a sharp
line at one end of each bearing shell.
b l o w with a 2 to 3 pound lead hammer.
The tangs on the lower bearing shell are
off-center and the tangs on the upper
3. Tighten the bolt to 300 lb-ft (407 Nm)
bearing shells are centered to aid correct
torque and strike again.
installation.
4. Tighten the bolt to 290-310 lb-ft
Various types of bearings have been
(393-421 Nm) torque.
layer
multiple
Currently
used.
copper-lead coplated or aluminum triplat-
NOTE
ed bearings are in use. These bearings
have an inner surface, call the matrix,
Do not strike the bolt after final
of copper-lead or aluminum. A thin de-
t o r q u e has been applied.
posit of babbitt is then plated onto the
matrix.
This babbitt overlay has excel-
lent resistance to friction, corrosion and
scoring tendencies which, combined with
the material of the matrix, provides im-
proved load carrying characteristics.
These bearings are identified by the sat-
in silver sheen of the babbitt when new
and a dull gray after being in service.
An oil hole in the groove of each upper
bearing shell, midway between the part-
ing lines, registers with a vertical oil
passage in the cylinder block. Lubricat-
ing oil, under pressure, passes from the
cylinder block oil gallery by way of the
bearing shells to the drilled passages in
the crankshaft, then to the connecting
rods and connecting rod bearings.
The lower main bearing shells have no oil
grooves; therefore, the upper and lower
bearing shells must not be interchanged.
F i g u r e 11B-86. M a i n B e a r i n g S h e l l ,
Caps and Thrust Washers