Cross-Drilled Crankshafts; Oversize Outside Diameter Main Bearing Shells - Lotus TURBO ESPRIT Service Manual

Page 50
SECTION EA
.
.
8.
(NOT Dry Sump Turbo)
Remove the ten nuts and washers to the outside of the sump mounting face,
followed by the ten large nuts and washen adjacent to the main journals;
a l l nuts should be released i n sequence working diagonally inwards from
thrs
outside. Remove the oil pick-up pipe and breather pipe from their locations
i n the main bearing housing and cylinder block. Lift off the main bearing
housing.
If
the housing i s tight, it i s
permissable t o tap lightly with a
rubber mallet to ease removal. Remove the spray shield from the rear of
the cylinder block.
9.
Lift out the crankshaft. Remove the main shell bearings from both the
bearing housing and the cylinder block. Remove the thrust washen from
the rear main bearing locations i n the cylinder block.
To Replace
1
.
Fit a new key to the front of the crankshaft to retain the sprocket.
2.
F i t
a new spigot bearing and new flywheel dowels i n the rear (flywheel)
end of the crankshaft.
Cross-dril led crankshafts
The 'standard' or non cross drilled crankshaft a s fitted to all front engined cars prio;
to engine no. 23749 (March 1987) has drillings from main bearings
1,2,4 & 5
through
to crankpins 1,2,3
& 4
to provide big end lubrication. Both upper and lower shells
for these main bearings are provided with a hole to admit oil from a drilling i n the
block, and a groove to provide an oil channel around which oil may flow to the big
end feed drilling i n the journal
.
l h e 'cross-drilled' crankshaft is'similar i n the above respect, but diffen as follows:
I n order to permit the use of plain lower main bearing shells with their increased
load bearing area, crank journals 1,2,4
& 5
are also 'cross-drilled' diametrically
across from the point where the big end feed drilling emerges. One end of this cioss
drilling i s therefore always i n communication with the oil supply channel i n the
grooved upper main bearing shell, maintaining big end lubrication throughout 360'
crankshaft rotation.
This 'cross-drilled' crankshaft i s fitted to a l l Esprit variants from engine no. 13277
(1976), and to Excel models from engine no. 23749 (1987). It i s
MOST IMPORTANT
to refer to the table i n section
TDA
(N/A) or TDB (Turbo) for the correct main
bearing shell configuration.
Oversize outside diameter main bearing shells
Whenever main bearing shells are to be replaced on any 907/912/910 engines,
it is most important to check whether the block assembly has been bored to accept
M.015 oversize outside diameter mainbearing shells on production.
0
APR 1987