TM 9-6115-604-34NAVFAC P-8-633-34Figure 9-32. Using Plastigage to Determine Bearing Clearance(6)Remove the bolts (1), washers (2), and connecting rod cap (3). Compare the width of the compressedPlastigage to the graduations on the Plastigage envelope (B. Figure 9-32). This is the connecting rod journalclearance and must conform to the specifications in Table 1-4.(7)If the clearance is under the specifications given in Table 1-4, remove the bearings shells (11, Figure 9-24) andcheck for oversize bearing shells, or the presence of foreign matter between the bearing shells and theconnecting rod (4) or cap (3).(8)If the clearance is over the specifications given in Table 1-4,install new bearing shells (11) and re-check theclearance. If the clearance is still excessive, rebuild the crankshaft (32) in accordance with paragraph 9-28.CAUTIONBefore Installing the connecting rod bolts (1) and washers (2), coat the bolt threads, theunderside of the bolt heads, and the washers with clean lubricating oil MIL-L-2104. Failure todo so will result In Improper torque and possible engine damage due to loosening of thebolts.(9)If the clearance is satisfactory, remove all traces of Plastigage from the bearing shell and crankshaft journal,lubricate the bearing shells and journal with a small amount of lubricating oil MIL-L-45199, and reinstall theconnecting rod cap (3), washers (2), and bolts (1). Tighten the bolts in accordance with Table 9-3.(10)Using a feeler gage, check the connecting rod side clearance. Connecting rod side clearance shall be 0.012 to0.020 inch (0.30 to 0.51 mm), and the rods must be free to move sideways on the crankshaft (32). i theconnecting rods do not move freely on the crankshaft, or the clearance is not to specifications, check forimproper bearing shell installation or crankshaft thrust surface wear. Rebuild a worn crankshaft in accordancewith paragraph 9-28.(11)Repeat steps c through e, above, for each connecting rod bearing shell to be replaced.9-60
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