Valve Seat Replacement

When valve seat is removed, replace with oversized [0.5 mm (0.020 in)] valve seat.

1. Bore out old seat until it collapses. Boring should not continue beyond the bottom face of the seat recess in cylinder head. Set the machine depth stop to ensure this. Refer to "VALVE SEAT ".
   CAUTION: Prevent to scratch cylinder head by excessive boring.
2. Ream cylinder head recess diameter for service valve seat.

   Oversize [0.5 mm (0.020 in)] 

   Intake : 38.500 - 38.516 mm (1.5157 - 1.5164 in) 

   Exhaust : 32.700 - 32.716 mm (1.2874 - 1.2880 in) 

   • Be sure to ream in circles concentric to valve guide center. This will enable valve to fit correctly.
     Fig 1: Identifying Cylinder Head Recess Diameter

     Courtesy of NISSAN MOTOR CO., U.S.A.
3. Heat cylinder head to 110° to 130°C (230° to 266°F) by soaking in heated oil.
   Fig 2: Heating Cylinder Head

   Courtesy of NISSAN MOTOR CO., U.S.A.
4. Provide valve seats cooled well with dry ice. Force fit valve seat into cylinder head.
   CAUTION:

   • Avoid directly touching cold valve seats.
   • Cylinder head contains heat. When working, wear protective equipment to avoid getting burned.
5. Finish seat to the specified dimensions using suitable tool. Refer to "VALVE SEAT ".
   CAUTION: When using valve seat cutter, firmly grip cutter handle with both hands. Then, press on the contacting surface all around the circumference to cut in a single drive. Improper pressure on with cutter or cutting many different times may result in staged valve seat.
   Fig 3: Cutting Valve Seat

   Courtesy of NISSAN MOTOR CO., U.S.A.
6. Using compound, grind to adjust valve fitting.
7. Check again for normal contact. Refer to "VALVE SEAT CONTACT ".