TATA PUNCH-SERVICE MANUAL

1.2L REVOTRON ENGINE 61 J. Connecting Rods : 1. Inspect the small end bush of connecting rod, and measure piston-pin bore. NOTE  Ensure that the connecting rod big end and small end axes are parallel to each other.  Ensure that the Centre distance between big end and small end is maintained within the specified limits. 2. Install connecting rod bearing caps without bearing shells. 3. Tighten connecting rod bearing caps mounting bolts to the specified torque. Connecting Rod – Small end Dimensions (Revotron 1.2T) Stage Parent Bore Diameter (mm) Bush – outer Diameter (mm) Normal 21.000 - 21.021 21.055 – 21.095 4. Check for twist and bend of connecting rod by using new piston pin at connecting rod small end. 5. Using feeler gauge, measure twist and bend of connecting rod with respect to vertical face of connecting rod alignment gauge in both vertical and horizontal plane at distance of 50mm, from the line joining centers of connecting rod big and small end bushes. NOTE  It is possible while installing the connecting rod bearing cap will be off center, by which dimension of connecting rod big end parent bore will be different in different conditions.  If difference exists, connecting rod bearing cap can be centralized by lightly tapping with mallet, in the required direction after loosening connecting rod bearing cap mounting nuts. 6. Install new pair of connecting rod bearing shell, depending on the size of crank pin journal diameter. Make sure the securing lugs are in the grooves of connecting rod and its bearing cap. 7. Install connecting rod bearing cap with bearing shell on connecting rod. Tighten connecting rod bearing cap mounting nuts to specified torque. NOTE  Correct bearing bore dimensions can be achieved if connecting rod big end parent bore dimension is maintained.  Measure pre-tension of connecting rod bearing shell with a feeler gauge after loosening connecting rod bearing cap mounting nuts. 8. Measure connecting rod big end parent bore dimension. If connecting rod big end parent bore is slightly more than maximum permissible limits, then the connecting rod can be reclaimed provided the wear is confined to connecting rod bearing cap. If the mating surface of the connecting rod bearing cap is slightly faced, then the parent bore should be given a finishing on a connecting rod boring machine. 9. If one or more connecting rods are to be replaced, the difference in weight of connecting rod should be within the permissible limit. Maintenance Limit (REVOTRON 1.2L) in mm Small end parent bore cylindricity 0.008 Connecting rod small end bush inside diameter (finished after installation) 18.007 / 18.020 Maximum permissible out of parallelism (bend) between connecting rod small end and big end parent bores. 0.015 Center to center distance between connecting rod small end and big end parent bores 138.8 ± 0.03 Maximum permissible twist of connecting rod 0.030 Connecting rod big end parent bore diameter 45.000 / 45.016 Big end parent bore and cylindricity 0.01 Bearing shell to be selected such that clearance is maintained as 0.027 - 0.066 Crush height of connecting rod big end bearing shells 0.025 - 0.055 Connecting rod big end axial play 0.05 - 0.35