TM5-6115-593-34NAVFAC P-8-631-34TO-35C2-3-463-20.001 inch (0.03 mm) or if chipped,flaked, or scored. See tabulated data inChapter 1 for shell thickness.(b) Total worn maximum oil clearanceshould not vary more than 0.001 inch(0.05 mm) between adjacent mainbearings. Refer to tabulated data inChapter 1.NOTEUnder no circumstances should anattempt be made to scrape bearingshells, nor should they be lapped or filedto increase oil clearances. A properlyfitted bearing will appear dull gray after areasonable period of service, indicatingit is running on an oil film. Bright spotsindicate metal-to-metal contact and blackspots indicate excessive clearance.(3) Connectingrods.(a) Magnaflux all connecting rods, caps andbolts; discard if cracks are detected.NOTEBe sure rod and cap are mated at alltimes.(b) Check rods for cracks with 1800-amperecurrent AC equipment or 1500-amperecurrent DC or rectified AC equipmentlongitudinally between plates.(c) Check rods for cracks with 3000 to 3400ampere-turns with AC equipment or2600 to 2800 ampere-turns with DC orrectified AC equipment in a coil.NOTEAmpere-turns is defined as the amperageflowing through the coil, multiplied bythe number of turns in the coil. Mostcoils contain four turns and thereforeonly 700 amperes need to be appliedwith DC equipment, or, 850 amperes withAC equipment.(d) Apply 1.5 percent wet solution whilecurrent is on. Make visual inspectionafter each application of current.(e) Assemble cap to rod and alternatelytighten nuts to operating tension bytorque method as specified in Chapter1.(f) Check crank pin bore with a dial boregauge or inside micrometers. Correctsize is important to provide correctbearing crush. New dimension after rodseparations are 4.0018 to 4.0028 inch(101.646 to 101.671 mm).(g) Check piston pin bushing diameter withplug gauge or with inside micrometers.Refer to tabulated data in Chapter 1.(h) Use rod checking fixture and locatingmandrel to check rod alignment.NOTEDifference in reading should not exceed0.015 inch (0.38 mm).(i) Check connecting rod bolts, bolt holes,and bolt pads. The bolt head must restsquarely on milled surfaces of the rod.(j) If connecting rod bolts have beentightened excessively, they may bepermanently stretched, in which casethey must be discarded. Discard bolt ifsmallest diameter is less than 0.540inch (13.72 mm).(k) Check bolt pilot OD; discard bolt if pilotis smaller than 0.6242 inch (15.855mm).(l) Discard all bolts and13-91
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