DETROIT DIESEL 53
allowing more oil, under pressure, to flow to the drilled
The main bearing shells are precision made and are
passage in the crankshaft.
replaceable without machining. They consist of an
upper shell seated in each cylinder block main bearing
support and a lower shell seated in each main bearing
cap. The bearing shells are prevented from endwise or
radial movement by a tang at the parting line at one end
of each shell.
The bearing caps are numbered 1, 2, 3, etc., indicating
their respective positions and, when removed, must
always be reinstalled in their original position.
The lower main bearing shells have no oil grooves;
therefore, the upper and lower bearing shells are not
The tangs on the lower bearing shells are off-center
while the tangs on the upper bearing shells are
The upper main bearing spell has six 1/4" holes and one
7/16" hole (Fig. 2) The additional holes in the upper
main bearing shell improves piston cooling by
Fig. 1. Main Bearing Shells, Bearing Caps and
Crankshaft Thrust Washers V-Type Engines
1972 General Motors Corp.
SEC 1.3.4 Page 1