Ford 2003 Mustang Workshop Manual page 921

SECTION 303-00: Engine System — General Information
GENERAL PROCEDURES
Valve —Seat Inspection
Valve and Seat Refacing Measurements
CAUTION: After grinding valves or valve seats, check valve clearance.
1. Check the valve head and seat.
Check valve angles.
Check margin width.
Refer to the appropriate section in Group
Be sure margin width is within specification.
2. Inspect for abnormalities on the valve face and seat.
2003 Mustang Workshop Manual
303 for the procedure.