TM  10-3930-643-34 GENERAL  SUPPORT  ENGINE,  FUEL,  EXHAUST  AND  COOLING  MAINTENANCE.  (cont) 13-2. Cylinder Head Assembly with Valves. CLEANING/INSPECTION/ASSEMBLY   (cont) 10. 11. 12. Using a feeler gage, install six new standard size seats (3) and inserts (4) with insert driver tool and an arbor press. Exert an even pressure of 500 lb-ft for five seconds. Proper depth of seat (3) and insert (4) counterbore is between 0.509 and 0.511 inches for intake and 0.455 and 0.459 inches for exhaust. Inspect for proper valve seat (3) mating. If surfaces do not mate correctly, oversize inserts (4) and seats (3) must be installed. NOTE The following procedure must be followed  before  installing  0.15  in oversize  seats  and  inserts. Measure bore of valve seat and insert counterbores  to  determine  if  cylinder head  (2)  must  be  machined.  If machining  is  necessary,  send  cylinder head (2) to depot maintenance. Bores must be within 2.011 and 2.012 inches for intake valves and 1.639 and 1.640 inches for exhaust valves. (Sheet 5 of 6) Co to sheet 6 13-12