During the cylinder head overhaul found some valves and seats surfaces worn.
There is nothing mentioned in manual book regarding valve/seat replacement interval. What is the criteria to discard valve and seat?
Check your engine's manual for parts highest allowable wear limits. You will see somethings similar to below table:
Measure your valves and seats sealing surfaces dimensions (width and outer diameter) as per wear table in manual book. Parts which exceed allowable limits should be discarded regardless of their running hours. Remember that valve and seat usually replaced together even if only one part in pair worn.
