TM-9-2815-202-34 Technical Manual for 8V71T Engines for M109 Howitzer Download
Page 239 of 670
TABLE 4-2 TM 9-2815-202-34 NOTE If one bearing shell is less than minimum thickness shown in Table 4-2, replace both bearing shells (upper and lower). (c) Using a micrometer and ball attachment, measure thickness of bearing shells (4) at point "C", 90 degrees from parting line. (1) ● ● (2) (3) Using micrometer, measure piston BEARING SHELL CONNECTING ROD THICKNESS skirt outside diameter parallel and BEARING *NEW BEARING MINIMUM WORN perpendicular to piston pin bore, SIZE THICKNESS THICKNESS obtain measurements at room STANDARD .1240"/.1245" .1230" temperature (70°F-21°C). Diameter .002” UNDERSIZE .1250'/.1255' .1240' must be 4.2428 to 4.2450 inches .010” UNDERSIZE .1290'/.1295' ,1280” (Diameter above and below pin bore .020" UNDERSIZE .1340'/.1345" .1330” may be 4.2414 inches). .030” UNDERSIZE .1390"/.1395" .1380” ‘Thickness 90° from parting line of bearing. NOTE Use feeler gage to check piston skirt to liner clearance. Use a spring scale attached to feeler gage to measure amount of force in pounds required to withdraw feeler gage from between piston and liner. Select feeler gage with thickness that will require six pounds pull to move. Piston to liner clearance will be 0.001 inch greater than thickness of feeler gage used. For example, a 0.004 inch feeler gage indicates 0.005 inch clearance when withdrawn with a six pound pull. Feeler gage must be perfectly flat and free of nicks and bends. With cylinder liner (1) installed in cylinder block, hold piston skirt (14) upside down in liner and check clearance in four places 90 degrees apart. Clearance must be 0.0045 to 0.0083 inch with new parts. Maximum clearance of 0.012 inch is allowed for used parts. If binding occurs between piston and liner, remove piston and examine piston and liner for burrs. Remove burrs with fine flat hone and recheck clearance. Change 1 4-137