Valve Seat Replacement

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

1. Bore out the old seat until it collapses. Boring should not continue beyond the bottom face of the seat recess in the cylinder head. Set the machine depth stop to ensure this.
2. Ream the cylinder head recess diameter for service valve seat.

   Oversize [0.5 mm (0.020 in)] (Service): 

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

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

   Fig 1: Identifying Cylinder Head Recess Diameter

   Courtesy of NISSAN NORTH AMERICA, INC.
   • Be sure to ream in circles concentric to the valve guide center.
   • This will enable valve seat to fit correctly.
3. Heat the cylinder head to 110° to 130°C (230° to 266°F) by soaking it in heated oil.
   Fig 2: Heating Cylinder Head To 110° To 130°C (230° To 266°F)

   Courtesy of NISSAN NORTH AMERICA, INC.
4. Cool the valve seats well with dry ice. Force fit the valve seat into the cylinder head.
   WARNING:

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

   Courtesy of NISSAN NORTH AMERICA, INC.
6. Grind to obtain the dimensions indicated as shown below.
   • Using compound, grind to adjust valve fitting.
     Fig 4: Identifying Valve Fitting Dimensions (Intake)

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     Fig 5: Identifying Valve Fitting Dimensions (Exhaust)

     Courtesy of NISSAN NORTH AMERICA, INC.
7. Check again for normal contact.