Measuring Valve Seat Contact Width

Produce a contact pattern on each valve using the following procedure:
1. Clean valve seat using a 45 degree carbide cutter. Remove only enough metal to clean the valve seat.
2. Apply a uniform coat of coloring compound, such as Prussian blue, or equivalent, to the valve face. There are many compounds available for this purpose and the manufacturer's instructions should be carefully followed to receive satisfactory results.
3. Press valve against valve seat, rotate the valve, at least one complete revolution, against the seat while applying slight pressure and then Remove valve.
4. The pattern produced on the valve face must be a continuous ring around the entire valve face. The ring should be in the center of the face and have a width of 1.0 to 1.4 mm (0.039 to 0.055 inch). If the ring is not continuous, the valve is not concentric and must be replaced.
5. If the coloring compound appears 360 degrees around the valve seat, the seat is concentric. If the coloring compound does not appear around the entire seat, the seat must be resurfaced.