490 / 1906
ENGINE
58
M. Connecting Rod :
1. Inspect connecting rod small end bush and if
necessary, replace it.
2. Check connecting rod small end parent bore
dimension.
Connecting Rod – Small end Dimensions
Stage
Parent Bore
Diameter (mm)
Bush – outer
Diameter (mm)
Standard
34H7
34.3 +/- 0.02
Standard
1
34.2H7
34.1 +/- 0.02
3. If necessary machine connecting rod small
end parent bore to next over size.
4. Ensure that connecting rod big end and small
end axis are parallel to each other and are
within specified limits.
5. Ensure that the centre distance between
small end to big end is maintained within
specified limit.
6. Smear oil on parent bore of connecting rod.
7. Install new bush in such a way that slits are
symmetrically positioned approximately in the
vertical axis.
NOTE
If required Machine the side faces of bush
to match the taper faces of connecting rod.
8. Finish connecting rod small end bush bore on
a connecting rod boring machine.
9. Alternately connecting rod small end bush
may be reamed. The end edges to be
chamfered / deburred manually.
10. Install connecting rod bearing caps without
bearing shells on connecting rod.
11. Tighten connecting rod bearing cap mounting
nuts to specified torque.
12. Ensure that identification numbers for
connecting rod and connecting rod bearing
cap are matched and notches for bearing
shells are on the same side.
13. Check twist and bend of connecting rod by
using new piston pin in connecting rod small
end bush.
14. Measure twist and bend of connecting rod
with feeler gauge with respect to vertical face
of the connecting rod alignment gauge in
vertical and horizontal plane at a distance of
50 mm from line joining centers of connecting
rod small end and big end bosses.
15. If necessary, straighten connecting rod in cold
condition. Since a slight clearance exists
between the connecting rod bolts and
corresponding connecting rod bearing cap
holes, it is possible that the connecting rod
bearing cap once removed may be installed
off center, due to which the dimension of the
connecting rod big end parent bore will be
different in different directions. If there is a
difference noticed in connecting rod big end
parent bore dimension, connecting rod
bearing cap can be centralized by lightly
tapping it with mallet in required direction after
slightly loosening connecting rod bearing cap
mounting nuts.
16. Check connecting rod big end parent bore
dimension.
17. If connecting rod big end parent bore is
slightly more than maximum permissible
limits, it is possible to reclaim the connecting
rod provided the wear is confined only to
connecting rod bearing cap. In such cases the
connecting rod bearing cap mating surface
can be slightly faced. The parent bore should
then be finished on a connecting rod boring
machine.
18. Ensure that the connecting rod big end and
small end axis are parallel to each other
within the specified limits. Centre to Centre
distance between connecting rod small end
and big end is maintained within specified
limits.
19. If one or more connecting rods are to be
replaced, ensure that difference in weight of
connecting rod in one engine is within
permissible limits.
20. Install new pair of connecting rod bearing
shell according to size of crank pin journal
diameter, making sure that securing lugs of
bearing shells are properly seated in grooves
of connecting rod and its bearing cap.