Crankshaft And Main Bearings - Perkins 4.108 Workshop Manual

SECTION H
Crankshaft and Main Bearings
H1
Description
The crankshaft runs in three pre-finished replaceable
thinwall, steel backed, aluminium tin lined bearings.
Crankshaft end lIoat is controlled by thrust washers
located either side of the rear main bearing. 0.0075 in
H2
(0.19 mm oversize) thrust washers are available which
if used on one side of the rear main bearing only
will reduce crankshaft end float by 0.0075 in (0.19
mm) and by 0.D15 in (0.38 mm) if used on both sides
The limits for the crankshaft end float are given on
Page 8.6.
The main bearing caps are numbered and are not
interchangeable. The main bearing shells are located
by means of tabs which locate in slots in the bearing
housings.
NOTE: Before renewal of the main bearings is
attempted make absolutely certain that the correct
replacements are available, reference to the relevant
parts list will ensure this, but for identification purposes
the new bearings should have an annular groove
machined in the inner (bearing) face along the centre
line of the feed holes, when the bearings are correctly
located these feed holes will correspond exactly with
those machined in the cylinder block.
On later 4.107 and 4.99 engines, the annular oil
groove in the main bearing parent bore (cylinder
block and bearing cap) has been deleted. Adequate
lubrication is maintained by repositioning the oil feed
holes radially in the shell bearings and continuing to
machine the annular groove in the bearing on the
centre fine of these feed holes.
These later type shell bearings may be used on both
early and later type engines, whereas the early type
of shell bearings must NOT on any account, be fitted
to later engines where the annular groove in the main
bearing parent bore has been deleted.