TM 10-3930-653-14&p (4)   CORRECTING (Grinding) VALVE SEATS Inspect  the  valve  seat  for  burning  or  faulty  contact. When  correcting  the  valve  seat,  first  check  the  valve guide for wear, and if excessively worn, replace the valve and then correct the valve seat. Fig. 4-39.  Grinding Valve Seats (1)   Correct valve seat with a seat cutter  or  seat  grinder and  finish  for  proper  fit  (proper  contact)  using  grinding compound. (2)   First cut to a 75  angle (around entire valve seat) and then bevel edge evenly to a 45° angle.  For proper fitting. apply   grinding   compound   (first   course   and   then   fine compound)  and  work  valve  back  and  forth  against  the valve seat until a smooth fit is provided, then apply oil for final fit. Fig. 4-40.  Fitting Valve Fig. 4-41.  Grinding Valve Fig. 4-42.  Dimensions of Valve Seats 4-2-4-4. VALVE (1)   Remove  all carbon from valve stem and valve seat and inspect valve stem for wear, binding, etc. and check valve seat for wear, recession, etc. caused by stem head wear, and correct or replace as required. Fig. 4-43.  Checking Valve Stem for Bending (2)   Correct  valve  seat  and  valve  with  a  valve  grinder. Replace valve if valve head thickness 4 - 29