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A
THE ENGINE
the old
one
from the sump and crankcase
faces. Smear
the face
of the
crankcase
joint with grease and
tit the
gasket.
Lift
the
sump
into position
on the
crankcase,
insert
the securing bolts, and tighten
them
evenly.
Section A.26
MAIN AND
BIG-El\'D
BEARINGS
Unless
the
bearing journals arc
badly
worn
the
big-end
bearings may
be
renewed
without removing the
crank-
shaft.
·
To
renew
the
main
bearings it is necessary to
withdraw the
crankshaft as
detailed in
Section
A.33.
Liners
are
used both for the main
and
the big-end
bearings, wh.icb
are
of the shim!ess
type and therefore
non-adjustable.
Big-end beariogs
Drain
the engine
oil and
remove
the
sump as in Section
A.25.
As
the
bearings are of
the
sbimless type it is essential
that
no attempt should
be
made to adjust
bearings which
are
worn.
Always
fit new bearings
in place
of worn
parts.
If the
crankshaft journals
are
found to be in a worn
condition it
is advisable to
fit
a new crankshaft, com-
plete
with
maio and big-end bearings,
as
supplied by
the
Factory.
Both
tbe
big-end
and
main
bearing liners are located
in
position
in the bearing housings
by a
small tag
on one
side of each
half-bearing;
it should be
noted
that
the
bearings are fitted so
that the
tags come on
the
same
joint edge of the bearing housing although on opposite
comers.
To detach the
big-end
bearings bend down the locking
strips so that the
bolt.
s may be removed.
Remove
the
connecting rod caps and
extract the
bearings.
Care
should be exercised
to
see that
the
bearing journals,
etc.,
are
thoroughly
cleaned before installing new bearings.
No
scraping is
required,
as the bearings are
machined
to give the correct
diametrical
clearance (see
'GENERAL
DATA').
Main
bearlng$
Remove
the engine
from the car and
remove
the clutch
and
fiywheel (Section
A.32)
and
the
gearbox
mounting
plate.
Remove
the sump,
oil strainer,
timing chain cover,
timing
chain,
and
engine front plate (Section A.23).
Remove the self-locking
nuts
securing
the main bearing
caps
to the cylinder
block.
Note that a
thrust washer
is fitted
one each side of the
centre
main
bearing
to take
the
crankshaft end-thrust.
These
thrust
washers each consist of
two semicircular
balves,
one half having a lug which is located in a
recess
in
the
detachable half of the
bearing and the
other
being
plain.
A
.
l4
When
fitting new
bearings
no
scraping is required
as
the
bearings are
machined
to
give the correct diametrical
clearance (see
'GENERAL
DATA').
In
the
case of a
'run'
bearing
it
is always essential to
clean
out thoroughly all the oilways in the crankshaft
and
block, wash out
the engine sump
with paraffin
(kerosene), and
clean
the oil pump
and
s ump strainer
to
ensure that
no particles
of metal are
left
anywhere
in the
lubricating
system.
Replaoe
each main bearing and
cap,
replacing the
thrust
washers
in their correct
positions
at the centre main bearing Y>'ith the
oil
grooves away
from the bearing.
Refit
the locking strip or locking
plates
to
each
bearing cap and bend them to lock the
bolts after
tightening.
[See
Addendum
for
additional
information.
]
Section
A.27
PISTONS
AND
CONNECllNG
RODS
Removal
Remove
the
cylinder head as in Section
A.l3. Drain
aod remove the sump and
oil
strainer
as
in
Section
A.25.
The
pistons and connecting rods m ust be
withdrawn
from
the
top
of the
cylinder block.
Unlock and
remove the
big-end bolts and
remove the
bearing caps. Release
the connecting rod from
the
crankshaft.
Withdraw the piston and connecting
rod from
the
top
of the cylinder block
and
refit
the
bearing cap. The
big-
end bearing caps are offset, and the caps on the big-ends
in
Nos.
I
and 3 cylinders are interchangeable
when
new,
as are those for Nos.
2
and
4
cylinders.
When used
parts
are replaced after dismantling it is essential that
they
should be fitted in
their
original
positions.
In
order
to
Fig.
A.12
A connecting rod bearing. Note tile bearing locating tab
MGA
(Twin
Gam).
Issue
3. 32403
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