Duramax LLY – PISTON/CONNECTING ROD INSTALLATION AND BEARING FIT

Verify correct piston and rod assembly. Be sure piston crown relief and notches in rod for bearing inserts are aligned (Figure 2-160). Install only one piston and connecting rod assembly at a time. This is necessary because rod bearing clearance must be checked with the bearing inserts dry. Check bearing clearance at each rod as it is installed.

Make sure the connecting rod caps are matched to their respective rods and are properly aligned. Failure to match and align the rod caps can result in premature bearing failure. Standard and undersize bearing inserts can be combined in one rod to obtain desired clearance. Just be sure to install the undersize insert in the rod cap.

CAUTION: Rod bearing clearance must be checked with the bearings dry (no lubrication). For this reason, the crankshaft must not be rotated during the measuring procedure. Otherwise, bearing damage will occur.

1. Lubricate cylinder wall, piston rings, and all surfaces of piston (except crown), with engine oil.

2. Verify that piston ring ends are properly spaced. Refer to spacing diagram (Figure 2-127).

3. Insert rod bearing halves in rod end and bearing cap. Install bearing dry. They will not be lubricated until after clearance check with plastic gauging material.

4. Install lengths of rubber hose on each connecting rod bolt. Hose will prevent cylinder wall scratches and nicks during piston installation (Figure 2-160).

5. Compress piston rings on #1 piston with compressor tool (Figure 2-161).

6. Rotate crankshaft until rod journal for number one piston is accessible.

7. Start number one piston in cylinder. Position rod end so it is aligned with crankshaft journal. Also be sure relief in piston crown is toward outside of engine.

8. Press piston downward into cylinder with hammer handle (Figure 2-161). Guide rod end onto crankshaft journal at same time.

9. Check rod bearing clearance as follows:
a. Place strip of plastic gauging material on crankshaft rod journal (Figure 2-162).
b. Install rod cap and bearing and tighten rod bolt nuts to 65 N•m (48 lb-ft).
c. Remove rod cap and measure gauging material with graduated scale on plastigauge envelope (Figure 2-162). Clearance should be 0.0017-0.0039 in. (0.045-0.100 mm).
d. If clearance is OK, proceed to next step. If clearance is not OK, use new standard or undersize rod bearings to obtain correct clearance. If combination of standard and undersize bearing inserts are required, install undersize insert in rod cap. Note that standard bearings provide more clearance than under size bearings.

10. Remove rod cap. Clean gauging material off crankshaft journal. Lubricate rod bearing halves and crankshaft journal with engine oil or assembly lube. Then reinstall rod cap and tighten new rod cap nuts to 48 lb-ft (65 N•m) torque.

11. Install remaining piston and connecting rod assemblies as described in steps 1. through 10.

12. Check connecting rod side play with feeler gauge (Figure 2-163). Insert gauge between connecting rods on same journal. Clearance should be 0.007-0.025 in. (0.17-0.63 mm).

NOTE: If side clearance is incorrect, rod caps or rod and piston may be installed in wrong position.

 

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