TM 9-2320-289-343-14.CHECKING MAIN BEARING CLEARANCE (Con’t).CAUTIONEnsure that main bearing caps (1) are fully seated before installing bolts (2and 3). Failure to follow this caution may result in damage to main bearingcaps.llNOTEInner bolts (3) are longer than outer bolts (2).Ensure that lubricating oil is applied to bolt (2 and 3) threads beforeinstallation,3.Using soft-faced hammer, tap main bearing #3 cap (1) into place and install 2 inner bolts (3)and 2 outer bolts (2). Tighten all bolts to 40 Ib. -ft. (54 N-m). Evenly tighten inner bolts again to110 Ib.-ft. (149 N.m). Evenly tighten outer bolts again to 100 Ib.-ft. (136 N.m).NOTEScale on envelope (7) of gaging plastic (6) should be used to measureclearance.DO NOT rotate crankshaft (5) while gaging plastic (6) is between mainbearing (4) and crankshaft.This will result in an inaccuratemeasurement.4.Remove 2 inner bolts (3), 2 outerbolts (2), and main bearing #3 cap(1). Measure flattened gaging plastic(8) at widest point to determine mainbearing clearance. Preferred mainbearingclearanceis 0.0018 in.(0.0457 mm) for main bearings #1-4and 0.0033 (0.0838 mm) for mainbearing #5. Clearance should be nomore than 0.005 in. (0.127 mm).5.Measure flattened gaging plastic (8)at each end and middle, andcomparereadings.Maximumdifference between ends and middle(taper)should be0.001 in.(0.025 mm). If there is taper,measurecrankshaft (5) journal.Replacecrankshaft ifthereisexcessive taper. (See paragraph3-1 5) Discard gaging plastic.6.If measurements in steps 4 and 5 are not correct, replace main bearing (4) (seeparagraph 3-1 5) and repeat steps 2-5. If still not within specifications, use undersized mainbearing. If smallest undersized bearing has been used, replace crankshaft (5). (Seeparagraph 3-1 5)TA506563 - 4 5
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