Cylinder Head, Valves and Manifolds GRIND VALVE SEATS IMPORTANT: Valve seats should never be cut. Cutting a valve seat can damage its sealing surface, which may result in leaks or valve/ seat failure. Valve seats should be ground and lapped. Lower Seat Surface 70° Valve Seat Upper Seat Surface NOTE: LIGHTLY grind valve seats for a few seconds only to avoid excessive valve seat width. 1 Seat Width 15° 1. Grind intake valve seat using a 30° seat grinder and exhaust valve seat using a 45° seat grinder. Follow tool manufacturers instructions.
Cylinder Head M82040A If valve recession exceeds maximum specifications or seats cannot be reconditioned, replace valves, valve seats if equipped and/or cylinder head. NOTE: Valve seat inserts are available for 4TN78T engine only. LAP VALVES NOTE: Use a rubber type lapping tool for valves without a lapping tool groove slit. 2. Measure valve seat width after grinding. If seat does not make proper contact, lap the valve into the seat: 3. If seat is too wide after grinding, grind lower seat surface using a 70° seat grinder until seat width is close to specifications. 1. Apply small amount of fine lapping compound to face of valve. 4.
Grind upper seat surface using a 15° seat grinder until seat width is narrowed to specifications. 2. Turn valve to lap valve to seat. 5. If valve seats are ground, measure valve recession and check contact pattern between the seat and valve with bluing dye. 3. Lift valve from seat every 8 to 10 strokes. Lap until a uniform ring appears around the surface of the valve face. 4. Wash all parts in solvent to remove lapping compound. Dry parts. 6. Lap valves. (See procedure in this group.) 5. Check position of lap mark on valve face. Lap mark must be on or near center of valve face. 1-30 4/7/95 AllTractorManuals.com Seat Grinder M82039A M82039A