Quantcast Crankshaft Journal Check

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to  avoid  distorting  them,  and  tapping  the  cap lightly  on  one  side  and  then  the  other. CRANKSHAFT   REMOVAL Once  the  bearing  caps  have  been  removed,  lift the  crankshaft  out  of  the  engine  block.  Usually one  or  two  people  do  this  seemingly  simple operation by hand. With larger crankshafts, use a  hoist  (fig.  3-25),  lifting  above  the  center  with a  rope  sling  around  two  of  the  throws. CAUTION Do  not  bang  the  crankshaft  around causing  damage  that  will  have  to  be repaired before the crankshaft may be put back  in  service. CRANKSHAFT  JOURNAL  CHECK The  preferred  method  of  measuring  crank- shaft  journals  is  as  follows.  Remove  the crankshaft  from  the  engine  block  and  clean  the surfaces  to  be  measured.  Using  the  appropriate outside   micrometer,   measure   the   journals   at several  points  around  and  across  the  bearing surface   (fig.   3-26).   Measurements   around   the journal will show if the journal is out of round. Those  measurements  across  the  surface  show  if the   journal   is   tapered.   Journals   that   are Figure 3-25.—Crankshaft removal using hoist. Figure 3-26.—Measuring the journals at different points around the diameter and along the length of the bearing surface. tapered or out of round more than .003 must be reground.  BE  SURE  THAT  YOU  ALWAYS REFER   TO   MANUFACTURER’S   SPECIFICA- TIONS   WHEN   PERFORMING   ANY   CRANK- SHAFT   WORK. CHECKING  OF  BEARING  FIT You  should  always  check  bearing  fit  or  oil clearance  when  installing  new  bearings.  When  the bearing  caps  are  off,  you  should  measure  the journals   so   that   you   can   detect   wear,   out   of roundness,  or  taper. You can check bearing clearance with either feeler stock or Plastigage. Plastigage is a plastic material that is flattened by pressure. The amount it  flattens  indicates  the  amount  of  clearance. Before  checking  bearing  clearance  with  Plasti- gage,  wipe  the  journal  and  the  bearing  clean  of oil. Then place a strip of the Plastigage lengthwise in the center of the bearing cap (fig. 3-26). Install the cap next and tighten it into place. When the cap is removed, you can measure the amount of flattening  of  the  strip  with  a  special  scale  (fig. 3-26).  Do  NOT  remove  the  flattened  strip  from the cap or the journal to measure the width, but 3-23



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