Figure 3-28.—Checking the alignment of a connecting rod. REPAIRING  CRANKSHAFTS  AND JOURNAL  BEARINGS The  repair  of  crankshafts  and  bearings  varies depending on the extent of damage. There is no doubt about the necessity for replacing such items as broken or   bent   crankshafts.   Out-of-round   journals   may   be reground and undersize bearing shells may be installed, but this requires personnel skilled in the use of precision tools. If a new shaft is available, it should be installed and  the  damaged  shaft  should  be  sent  to  a  salvage reclamation  center.  Under  certain  conditions,  scored crankshaft  journals  or  damaged  journal  bearings  may  be kept in service if proper repair is performed. Repair  of  SCORED  JOURNALS  depends  on  the extent of scoring. If a crankshaft has been overheated, the effect of the original heat treatment will have been destroyed.  In  this  case,  the  crankshaft  should  be replaced. If  journal  scoring  is  only  slight,  you  can  use  an oilstone  for  dressing  purposes  if  you  take  precautionary measures with respect to abrasives during the procedure. During  the  dressing  operation,  plug  all  oil  passages within the journal and those connecting the mainbearing journal and the adjacent connecting rod journal. In   the   dressing   procedure,   use   a   fine   oilstone, followed with crocus cloth, to polish the surface. After dressing  journals,  always  wash  them  with  diesel  oil. This  procedure  must  include  washing  the  internal  oil passages as well as the outside journal surfaces. Some passages are large enough to accommodate a cleaning brush; smaller passages can be cleaned by blowing them out  with  compressed  air.  Always  dry  the  passages  by blowing compressed air through them. NEVER STOW A CRANKSHAFT OR BEARING PART ON ANY METAL SURFACE.  When you remove a shaft from an engine, place it on a wooden plank with Figure 3-29.—Using a strain or deflection gauge between crank webs. all  journal  surfaces  protected.  If  the  shaft  is  to  be exposed for some time, protect each journal surface with a  coating  of  heavy  grease.  Always  place  bearings  on wooden boards or clean cloths. CRANKSHAFT  overhaul  consists  of  an  inspection, servicing for scoring and wear, and a determination of each crank web deflection. Take crank web deflection readings according to the Planned Maintenance System (PMS). A strain gauge, often called a crank web deflection indicator, is used to take deflection readings. The gauge is  merely  a  dial-reading  inside  micrometer  used  to measure the variation in the distance between adjacent crank webs as the engine shaft is barred over. Figure 3-29 shows a strain gauge between crank webs. When you install the gauge, or indicator, between the webs of a crank throw, be sure to place the gauge as far  as  possible  from  the  axis  of  the  connecting  rod journal.  Rest  the  ends  of  the  indicator  in  prick-punch marks in the crank webs. If these marks are not present, make  them  so  that  the  indicator  can  be  placed  in  its correct position. Consult the manufacturer’s technical manual for the proper location of new marks. Readings  are  generally  taken  at  the  four  crank positions: top dead center, inboard, near or at bottom dead center, and outboard. In some engines, it is possible to  take  readings  at  bottom  dead  center.  In  others,  the connecting  rod  may  interfere,  making  it  necessary  to take  the  reading  as  near  as  possible  to  bottom  dead center without having the gauge come in contact with the  connecting  rod.  When  the  gauge  is  in  its  lowest 3-19