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2B.14 Engine removal and overhaul procedures
10.3 Fitting the centre main bearing
upper shell
inner surfaces with a clean rag - they must be
kept spotlessly clean.
3 Clean the rear surface of the new bearing
shells with a rag and lay them on the bearing
saddles. Ensure that the orientation lugs on
the shells engage with the recesses in the
saddles and that the oil holes are correctly
aligned (see illustration). Do not hammer or
otherwise force the bearing shells into place.
It is critically important that the surfaces of the
bearings are kept free from damage and
contamination.
4 Give the newly fitted bearing shells and the
crankshaft journals a final clean with a rag.
Check that the oil holes in the crankshaft are
free from dirt, as any left here will become
embedded in the new bearings when the
engine is first started.
5 Carefully lay the crankshaft in the
crankcase, taking care not to dislodge the
bearing shells.
Running clearance check
6 When the crankshaft and bearings are
refitted, a clearance must exist between them
to allow lubricant to circulate. This clearance
is impossible to check using feeler blades, so
Plastigage is used. This is a thin strip of soft
plastic that is crushed between the bearing
shells and journals when the bearing caps are
tightened up. The change in its width then
indicates the size of the clearance gap.
7 Cut off five pieces of Plastigage, just
shorter than the length of the crankshaft
journal. Lay a piece on each journal, in line
with its axis (see illustration).
6 Wipe off the rear surfaces of the new lower
10.7 Lay a piece of Plastigage on each
journal, in line with its axis
half main bearing shells and fit them to the main
bearing caps, again ensuring that the locating
lugs engage correctly.
9 Wipe the front surfaces of the bearing shells
and give them a light coating of silicone
release agent - this will prevent the Plastigage
from sticking to the shell. Fit the caps in their
correct locations on the bearing saddles,
using the manufacturers markings as a guide.
Ensure that they are correctly orientated - the
caps should be fitted such that the recesses
for the bearing shell locating lugs are on the
same side as those in the bearing saddle.
10 Working from the centre bearing cap,
tighten the bolts one half turn at a time until
they are all correctly torqued to their first
stage only. Do not allow the crankshaft to
rotate at all whilst the Plastigage is in place.
Progressively unbolt the bearing caps and
remove them, taking care not to dislodge the
Plastigage.
11 The width of the crushed Plastigage can
now be measured, using the scale provided
(see illustration). Use the correct scale, as
both imperial and metric are printed. This
measurement indicates the running clearance
- compare it with that listed in Specifications.
If the clearance is outside the tolerance, it
may be due to dirt or debris trapped under the
bearing surface; try cleaning them again and
repeat the clearance check. If the results are
still unacceptable, re-check the journal
diameters and the bearing sizes. Note that if
the Plastigage is thicker at one end, the
journals may be tapered and as such, will
require regrinding.
10.11 Measure the width of the crushed
Plastigage using the gauge provided
12 When you are satisfied that the
clearances are correct, carefully remove the
remains of the Plastigage from the journals
and bearings faces. Use a soft, plastic or
wooden scraper as anything metallic is likely
to damage the surfaces.
Crankshaft - final refitting
13 Lift the crankshaft out of the crankcase.
Wipe off the surfaces of the bearings in the
crankcase and the bearing caps. Fit the thrust
bearings either side of the No 3 bearing
saddle, between cylinders No 2 and 3 (see
illustration). Use a small quantity of grease to
hold them in place; ensure that they are
seated correctly in the machined recesses,
with the oil grooves facing outwards.
14 Liberally coat the bearing shells in the
crankcase with clean engine oil (see
illustration).
15 Lower the crankshaft into position so that
No 2 and 3 cylinder crankpins are at TDC;
No 1 and 4 cylinder crankpins will then be at
BDC, ready for fitting No 1 piston.
16 Lubricate the lower bearing shells in the
main bearing caps with clean engine oil, then
fit the thrustwashers to either side of bearing
cap No 3, noting that the lugs protruding from
the washers engage the recesses in the side
of the bearing cap (see illustration). Make
sure that the locating lugs on the shells are
still engaged with the corresponding recesses
in the caps.
17 Fit the main bearing caps in the correct
order and orientation - No 1 bearing cap must
be at the timing belt end of the engine and the
bearing shell locating recesses in the bearing
10.13 Thrustwashers fitted to the
No 3 bearing saddle
10.14 Liberally coat the bearing shells in
the crankcase with clean engine oil
10.16 Fitting the centre main bearing cap