Casing unit: crankcases
Shimming the crankshaft
After fitting the new main bearings, proceed as follows to determine the total shimming
“
S
“
.
Measure
“
A
”
between the crankshaft surfaces that contact the bearings.
Measure the depths
“
P1
”
and
“
P2
“
corresponding to the distance between the mating surfaces of the two casings and
the contact surfaces of the inner races of the bearings;
Add a pre-load of
0.30
mm. This will compensate the additional end float resulting from heat expansion when casings
reach operating temperature;
This gives: S=P1+P2+0.30-A.
To calculate the amount of shimming required for each casing, note that:
S=S1+S2
where
“
S1
“
and
“
S2
“
represent the shimming for the casings 1 and 2.
Considering shaft alignment, this gives:
S1=P1+0.15
–
A/2;
And, finally, the second shimming: S2=S-S1.
Practical shimming procedure for the crankshaft
Below is a practical shimming procedure allowing to correctly calculate crankshaft shims.
Install a shim (R) of min. thickness (
1.90
mm) on each side of the crankshaft to avoid contact between crank web
and engine block.
Fit crankshaft into casing and close engine block.
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