First, use some prussian blue and observe where the old seat contacts the\nvalve face. If the old seat is on the valve face with no overlap, then\nproceed with the simplified procedure below:\n\nUse a 15 degree stone and cut the old seat in half.\nGrind the new seat. You want intakes to be the width of a dime and the\nexhaust the width of a penny (nickel in the case of auto engines).\nFinish by using grinding fine grit grinding past to lap the valves.\n\nCheck your work by pouring solvent into the inverted combustion chamber\nwith the spark plug installed. There should be no leakage through the\nports.\n\nYou will find the new seat meets the valve face in the same area as the old\nseat. This procedures saves countless trial and error grindings to get the\nseat in place at the correct width.