ENGINE DIVISION SERVICE MANUAL TM 5-4210-230-14&P-1 ENGINE To  obtain  proper  bearing  assembly  with  the  correct "crunch,"  care  must  be  taken  when  tightening  the  clamping bolts and nuts to make sure they are drawn down alternately and evenly using a tension wrench and tightened as specified. Rod   caps   or   blocks   must   not   be   filed,   lapped   or reworked  in  any  other  manner  in  order  to  reduce  clearance. While such practice may make a tighter fit at top and bottom, it    will    result    in    an    out-of-round    bore    and    bearing    shell distortion. Main and connecting rod bearings are designed with the "spread" (width across the open ends) slightly larger than the diameter of the crankcase bore or connecting rod bore into which they are assembled.  For example, the width across the rod  bearing  not  in  place  is  approximately  .025"  more  than when  the  bearing  is  in  position.    This  condition  is  designed into  the  bearing  to  cause  it  to  spread  outward  at  the  parting line  when  "crush"  load  is  applied  by  tightening  the  nuts  and bolts.  Some of this "snap" may be lost in normal use, but the bearing  need  not  be  replaced  because  of  a  nominal  loss  of this condition. This condition causes the bearing to fit snugly in the respective  bore.    The  bearing  must  be  "snapped"  or  lightly forced into its seat, Figure 125. Fig. 125  Illustrating Bearing Spread 1. O.D. of bearing 2. Spread of bearing when installed before installation is the same as the diameter of the crankshaft or conn. rod bore. BEARING SPREAD DIMENSIONS Bearing O.D. Specified Spread of (Installed) Spread Bearing "A" Fig. 122 Connecting Rod Bearings 2.6245-2.6250 .030-.0305 2.6545-2.6555 Main Bearings No's 1, 2, 4 & 5 3.3160-3.3152 .0200-.0208 3.336 No.  3 (Thrust) 3.3160-3.3152 .0020-.0168 3.318-3.332 B.  Fitting Main Bearings To  obtain  an  accurate  reading  using  the  Plastigage method  of  checking,  all  bearing  caps  must  be  in  place  and torqued to specifications. 1. Remove one bearing cap and insert. Remaining caps are left tight while checking the fit of this bearing. 2. Wipe   the   oil   from   all   contact   surfaces   such   as crankshaft journal, bearing insert, bearing caps, etc. 3. Place   a   piece   of   Plastigage   the   full   width   of   the bearing surface on the crankshaft journal (or bearing cap   insert)   approximately   ¼ "   off   center.      Install bearing  cap  and  tighten  cap  bolt  to  recommended torque. NOTE:    Do    not    turn    crankshaft    while    making check with Plastigage. 4. Remove bearing cap and insert. 5. Do   not   disturb   Plastigage.      Using   the   Plastigage envelope, measure the widest point of the Plastigage, Figure   126.      This   reading   indicates   the   bearing clearance in thousandths of an inch. 6. If  the  bearing  clearance  is  not  within  specifications, the   crankshaft   must   be   reground   and   underside bearings installed. CGES-210  Page 50 PRINTED IN UNITED STATES OF AMERICA