TM 10-3950-672-24-2
Crankshaft and Main Bearings
The crankshaft is a balanced, forged steel unit. Four-
cylinder engines have 5 main bearings. Six-cylinder
engines have 7 main bearings. The lower bearing shells
are all the same. All of the upper bearing shells are also
the same with the exception of the journal adjacent to
the rear one. The next to the last journal is fitted with a
flanged upper bearing shell. The flanges control the end
thrust of the crankshaft.
The upper bearings have three holes in them. The
middle hole receives oil from the main oil rifle. One of
the adjacent holes is aligned with drilling to the camshaft
journal and serves as an orifice for lubrication flow to
the journal. The other adjacent hole supplies oil for
piston cooling. The hole does not align perfectly with
the cooling nozzle. The hole is off-set to keep it away
from the highly loaded bearing area.
Note: Oversize service main bearings are available for
reground crankshafts.
Cylinder Block
We have discussed the cylinder block relative to cooling and lubrication in those respective systems. We have also
discussed the interfaces of some of the above power functions with the block. This discussion will cover the remaining
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