TM  10-3930-638-24&P 4-2.   ENGINE   MAINTENANCE   (cont) b.  Cylinder  Head  and  Valves  (cont). STEP LOCATION ITEM ACTION REMARKS VALVES AND VALVE SEAT REFACING 10 Refacing a. Protractor Set At 44 degree angle machine b. Chuck Clean c. Grinding wheel Dress 11 Valves (6 and 7) Grind  lightly Grinding angle is 44 degrees NOTE Replace any valve that has a thin margin or edge. If margin on ground valve is less than half margin on new valve, replace that valve. 12 Valve  seats Grind  lightly Grinding angle as shown. Use precision seat and  inserts  (14) grinder. Take very light cuts to remove just enough metal to obtain a smooth seat finish. 13 Valves (6 and 7) a. Apply valve Use Prussian Blue. Apply to valve face bluing b. Install In cylinder head (8). Rotate valve in seat c. Remove Check contact area on valve face and seat. Bluing will be removed from valve face where  contact  was  made  with  seat.  Cor- rect  and  incorrect  indications  along  with remedial  procedures  are  shown  below 4-16