TM 5-3825-226-24 CRANKSHAFT CRANKSHAFT Reconditioning   of   the   crankshaft   can   be   done   by grinding the "journals" (bearing surface on the crankshaft   for   the   connecting   rod   bearings   and   main bearings)  .010  in.    (0.25  mm),  .020  in.    (0.51  mm)  or .050 in.  (1.27 mm) "undersize" (smaller than the original size). The diameter of the "journals' for the connecting rod bearings  is  2.7496  .0006  in.    (69.840  0.015  mm).    The diameter   of   the   "journals"   for   the   main   bearings   is 3.4995 ±  .0006 in.  (88.887 ±  0.015 mm).  The minimum permissible diameter of the "journals" for the connecting rod    is    2.7486    in.        (69.814    mm).        The    minimum permissible   diameter   of   the   "journals"   for   the   main bearings  is  3.4985  in.    (88.862  mm).    Measure  each "journal"  in  several  places  around  the  diameter  to  find the   maximum   wear   point.      If   the   diameter   of   any "journal"    is    smaller    than    the    minimum    permissible diameter,  grind  all  of  the  "journals."  Before  grinding  a crankshaft,  check  the  crankshaft  for  being  straight.    To check a crankshaft for being straight, support each end main    bearing    "journal"    in    V-blocks.        Using    a    dial indicator, position the indicator at the zero reading then measure  the  total  indicator  reading  at  the  other  three main  bearing  "journals."  The  maximum  total  indicator reading is .008 in.  (0.20 mm) at the center main bearing "journal" and .004 in.  (0.10 mm) at the other two main bearing "journals." If total indicator reading is more than that   given   but   less   than   .030   in.      (0.76   mm)   the crankshaft     can     be     "straightened"     (made     straight). Before "straightening" (making straight) a crankshaft get temperature of the crankshaft to 400°F (204°C).  For the specifications  for  grinding  a  crankshaft,  see  the  topic CRANKSHAFT GRINDING SPECIFICATIONS. With  the  crankshaft  installed  in  the  cylinder  block, check the end play for the crankshaft.  End play for the crankshaft   is   .003   to   .010   in.      (0.08   to   0.25   mm). Maximum   permissible   end   play   for   the   crankshaft   is .014 in.  (0.36 mm). NOTE:    If  end  play  for  the  crankshaft  is  more  than  the maximum  permissible  end  play,  check  the  crankshaft thrust bearing. CRANKSHAFT GRINDING SPECIFICATIONS The dimensions and finish for grinding crankshafts are as follows: Diameter (A) for connecting rod bearing journals is; .010 in.  (0.25 mm) Undersize..................................2.7396 ±  .0006 in. (69.586 ± 0.015 mm) .020 in.  (0.51 mm) Undersize .................................2.7296 ±  .0006 in. (69.332 ± 0.015 mm) .050 in.  (1.27 mm) Undersize .................................2.6996 ±  .0006 in. (68.570 ± 0.015 mm) Surface finish must be 10 micro inches (0.25 micrometers) or less. Radius (B) must be .100 + .010 in.  (2.54 - 0.25 mm). Surface finish must be 63 micro inches (1.6 micrometers) or less. The radius must blend smoothly with the newly machined journals. DIMENSIONS FOR GRINDING A.  Diameter of connecting rod bearing journals.  B. Radius   on   connecting   rod   bearing   journals.      C. Width to grind journals for the connecting rods.  D. Diameter  of  main  bearing  journals.    E.    Radius  on main  bearing  journals.    F.    Width  to  grind  journals for the main bearings. Width (C) is 2.314 ± .003 in.  (58.77 ±  0.08 mm) Diameter (D) for main bearing journals is: .010 in.  (0.25 mm) Undersize..................................3.4895 ±  .0006 in. (88.633 ± 0.015 mm) .020 in.  (0.51 mm) Undersize..................................3.4795 ±  .0006 in. (88.379 ± 0.015 mm) .050 in.  (1.27 mm) Undersize..................................3.4495 ±  .0006 in. (87.617 ± 0.015 mm) 3-384