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Page Title: Fig. 98 Connecting Rod Cap and Bolt Details
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ENGINE DIVISION SERVICE MANUAL TM 5-4210-230-14&P-1 ENGINE to a specified torque is to obtain tension in the bolt, Figure 98, which   in   turn   developes   a   clamping   load   or   preload   that exceeds any possible loading imposed on parts due to engine RPM.  In other words, the connecting rods must "hang on" to the crankshaft and suffer all the strains of intertia and cylinder combustion impulse without permitting the least movement or flexing of the rod cap, bolts or nuts.  At the same time, torque applied  must  be  within  the  capacity  of  the  parts  (bolt,  nut, caps and connecting rods) to withstand these loads. Fig. 98  Connecting Rod Cap and Bolt Details 1. Friction 4. Clamped 2. Torque 5. Tension 3. Washer In  tightening  connecting  rod  bolts  and  nuts  to  their specified torque figure, a definite loading is obtained between the  connecting  rod  and  cap.    Specially  designed  bolts,  nuts and washers manufactured from selected materials permit the application  of  this  loading  without  undue  stretching  of  bolts. There is a relationship between the torque specifications and clamping    effect    or    load    to    be    applied    providing    certain conditions exist. These conditions center largely around the belt itself and its care, pointed out as follows: 1. Bolt and Nut Thread Condition: Threads  that  are  dry,  excessively  rough,  battered  or that are filled with dirt require considerable effort just to rotate the nut.  Then when the clamping load is developed or the bolt tension  is  applied,  the  torque  reading  mounts  rap            o-idly (due    to    thread    friction)    to    the    specified    figure    without approaching the desired bolt tension and maximum clamping effect.    Under  these  conditions  the  desired  torque  reading  is obtained,    but    the    clamping    effect    might    be    far    below requirements,  leading  to  bearing  failure  or  to  connecting  rod bolt  breakage.    The  proper  bolt  tension  and  clamping  effect can never be attained if the nut is dry. The nut and bolt must have a film of lubricant in the thread section to be considered lubricated.  It is recommended that new connecting rod bolts, nuts  and  washers  be  used  during  reassembly.    Due  to  the close fit of the connecting rod nuts on the bolts, the slightest thread  imperfection  increases  the  friction  to  the  extent  that incorrect bolt tension is likely. Connecting rod bolts and nuts must be cleaned of all foreign matter including the anti-rust materials that may be in the threads.  Apply light engine oil to the threads to lubricate before installation. 2. Tightening    of    Connecting    Rod    Bolts,    Nuts    and Washers Tighten  the  connecting  rod  bolts,  nuts  and  washers alternately   with   the   torque   wrench   to   the   specified   torque. Then release the torque load to zero and retorque to specified torque.  See "Torque Chart." If nut is overtightened enough to stretch the bolt, the nut and bolt both must be replaced.  Use new rod bolts, nuts and flat washers in major engine overhaul. The  application  of  specified  torque  to  any  particular bolt  or  nut  which  serves  to  hold  or  clamp  two  parts  together should  be  accomplished  with  a  torque  wrench  known  to  be accurate. Piston Rings The  pistons  used  in  the  V-type  engines  have  three piston  rings  located  above  the  piston  pin.    The  compression rings  are  located  in  the  top  grooves  while  the  lower  groove accommodates the oil control ring.  Select the proper rings for the size of pistons to be used. Prior to installing the rings on the pistons, each ring must be checked for proper ring gap.  Push the ring down into the cylinder bore making sure the ring CGES-210  Page 36 PRINTED IN UNITED STATES OF AMERICA

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