position,   the   dial   will   be   upside   down,   making   it necessary  to  use  a  mirror  and  flashlight  to  obtain  a reading. NOTE:  Once  you  have  placed  the  indicator  in position for the first deflection reading, do not touch the gauge   until   you   have   taken   and   recorded   all   four readings. Deflection   readings   are   also   used   to   determine correct alignment between the engine and the generator or between the engine and the coupling. However, when determining   alignment,   you   should   take   a   set   of deflection readings at the crank nearest the generator or the coupling. In aligning an engine and generator, you may need to install new chocks between the generator and  its  base  to  bring  the  deflection  within  the  allowable value.  You  may  also  need  to  shift  the  generator horizontally  to  obtain  proper  alignment.  To  align  an engine and a coupling, first, correctly align the coupling with the drive shaft; then, properly align the engine to the  coupling,  rather  than  aligning  the  coupling  to  the engine. BEARING  TROUBLES Bearings  become  a  continual  source  of  trouble unless  personnel  entrusted  with  operating  the  engine follow  the  recommended  operation  and  maintenance procedures  exactly. Severe bearing failures are indicated during engine operation  by  a  pounding  noise  or  by  the  presence  of smoke  in  the  vicinity  of  the  crankcase.  Impending failures  may  sometimes  be  identified  by  a  rise  in  the lubricating   oil   temperature   or   a   lowering   of   the lubricating oil pressure. Impending bearing failure may be  detected  during  periodic  maintenance  checks  or during  engine  overhauls  by  inspection  of  the  bearing shells and backs for pits, grooves, scratches, or evidence of  corrosion. The  indication  of  an  impending  failure  does  not necessarily  mean  that  the  bearing  has  completed  its useful life. Journal bearings may perform satisfactorily with  as  much  as  10  percent  of  the  load-carrying  area removed by fatigue failure. Other minor casualties may be repaired so that a bearing will give additional hours of satisfactory service. Bearings  should  not  be  rejected  or  discarded  for minor  pits  or  minute  scratches;  however,  areas indicating metallic contact between the bearing surface and the journal do mean replacement is needed. Use a bearing scraping tool to smooth minute pits and raised Figure 3-30.—Using a torque wrench to tighten a main bearing. surfaces. After working on bearings, make every effort to ensure that the bearing surfaces are clean. This also applies  to  the  bearing  back  and  the  connecting  rod journal  Place  a  film  of  clean  lubricating  oil  on  the journals  and  the  bearing  surfaces  before  you  reinstall them. INSTALLING JOURNAL BEARINGS Always check the markings of the lower and upper bearing  halves  so  you  install  them  correctly.  Many bearings are interchangeable when new, but once they have become worn to tit a particular journal they must be  reinstalled  on  that  particular  journal.  You  must  mark or stamp each bearing half with its location (cylinder number)  and  the  bearing  position  (upper  or  lower)  to prevent  incorrect  installation. You must also pull the connecting rod bearing cap nuts down evenly on the connecting rod bolts to prevent possible  distortion  of  the  lower  bearing  cap  and consequent damage to the bearing shells, cap, and bolts. Use a torque wrench (fig. 3-30) to measure the torque applied to each bolt and nut assembly. Apply the same torque to each bolt. If a manufacturer recommends the use of a torque wrench, the specified torque will be listed in the manufacturer’s technical manual. Another method for pulling down the nuts evenly is to stretch each bolt an equal amount and measure the distance  from  end  to  end  of  the  bolt  before  and  after tightening. Figure 3-31 shows the type of gauge used, 3-20