ARMY TM 9-2815-257-24 AIR FORCE TO 38G1-128-2 MARINE CORPS TM 10155A/2815-24/3 5-22 5-10.  PISTON AND CONNECTING ROD MAINTENANCE  -  cont. 2. Measure  the  outside  diameter  (OD)  of  piston, approximately  1/2  inch  from  the  bottom  (Figure 5-13).    OD  must  be  3.0591  inches  (77.70  mm), minimum.  Replace piston if out of limits. 3. Measure  the  internal  diameter  (ID)  of  the  piston pin hole in piston.  ID must be 0.8295 inch (21.07 mm), maximum.  Replace piston if out of limits. 4. Measure  the  OD  of  piston  pin  (12,  Figure  5-15) along the length of the pin.  OD must be 0.8232 inch (20.91 mm), minimum.  Replace piston pin if out of limits. Figure 5-13.  Piston Inspection 5. Using new piston ring set, measure the clearance between  piston  rings  and  piston  grooves  (Figure 5-14).  Side clearance must be 0.0059 inch (0.15 mm),   maximum.      If   clearance   exceeds   limit, replace piston. D.    INSTALLATION. 1. Install   new   ring   set   into   piston   ring   grooves.   Mount  rings  with  end  gaps  staggered  120 apart (see  Figure  5-16).    Make  sure  that  rings  move smoothly in grooves. Use  extreme  caution  when  handling hot   components.      Wear   protective gloves.      Failure   to   observe   this warning    can    result    in    injury    to personnel. 2. To install piston pin (12, Figure 5-15) into piston (8)  and  connecting  rod  (9),  heat  components  to 158  to  176 F  (70  to  80 C).    Match  marks  on piston and connecting rod and install connecting rod into piston.  Install piston pin (12) and allow components to cool. Figure 5-14.  Piston Ring Groove Clearance WARNING