First measure the valve stems at specific points before starting service and repair work to check for diameter compliance; new components must be installed for valves out of specifications. Examine the valve areas by inspecting the stem end for grooves or scoring, the valve face together with edge for pits as well as scores, the valve head for signs of burning, erosion, warpage and cracking while checking the valve margin for wear. Post-valve seat or valve grinding operations check the valve clearance together with valve head and seat condition and valve angles and margin width for compliance with specifications. The valve face and seat display any abnormalities which require installation of a brand new cylinder head assembly.