Main And Connecting Rod Bearings; Crankshaft Journal Specifications - Ford 1949-50-51 F-Series Truck Shop Manual

12 Chapter I- General Engine Repair
(3) GRINDING CRANKSHAFT JOURNALS .
Calculate the correct undersize from the crankshaft
dimension given above.
EXAMPLE :
1/ Ih e main bearing jo urnal on an E
Series Engine crankshaft will " clean
up"
/) el o re
it
is f(rou Ilcl to 2.499 -0.010
=
2.489 inc/, es diam·
ete r, finish it to 'hat diamete r and ins/all 0.010
undersize bearings .
Undersize bearings are available in 0.002, 0.0 10,
0.020, and 0.030 inch sizes for Hand M series engines
and 0.002, 0.010, 0.020, 0.030, and 0.040 inch sizes for
R and E series engines.
NOTE : On
lat e lllodel E series engines a series oj
selecti ve fit bearings are used instead
0/
t/, e 0.002
in ch undenize bearing.
Always reproduce the same radii that existed orig-
inally
10
the corners of the pin or journal. T oo small
a radius may result in crankshaft failure, whitt: too large
a radius w11l result in bearing failure.
After grinding, polish the pin or journal with No.
320 grit emery cloth and engine oil. Crocus cloth tnay
also be used.
b. Main and Connecting Rod
Bearings.
Steel backed copper-lead insert bearings are used in
the main bearing supports and connecting rods. These
Fig . 'S-Bearing Scratched bv D,n
Table 4-Crankshofl Journal Specifications
lDiame ter ( Inches)
Engine
Main J ournal
Front and Center
R ear Crankpin
E 2.8735-2.8740 2.8730-2.8735
2.3995-2.4000
R 2.4982-2.4990 2.4982-2.4990 2.1382-2.
1390
HorM
2.8732-2.8740 2.8732-2.8740 2.2980-2.2988
bearings are held in place with inde ntations on the end
of the insert which locate in machined notches in the
cyl inder block and connecting rod caps when installed.
Care should be used in fitting bearings SInce the
crankshaft carries the entire engine load. Lubrication
must be maintained or the bearings will wear out
rapidly with possible damage to the crankshaft journals.
Be sure the oil holes in the bearing line up with those
in the bearing bore.
Crankshaft end thrust is controlled by the rear main
bearing flange.
Bearing inserts are precision manufactured and are
ordered by size to re-establish the manufacturer's toler-
ance when the engine is overhauled.
Main bearing inserts th at are scratched. show fatigue
pockets, or have the overlay wiped out, should be re-
placed.
Fig. 16-Fatigue Failure
0'
Bearing