Valve Seat Replacement

When valve seat is removed, replace with an 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 the cylinder head. Set the machine depth stop to ensure this.
Fig 1: View Of Seat Recess
Courtesy of NISSAN MOTOR CO., U.S.A.
2. Ream cylinder head recess diameter for service valve seat.
   1. Oversize : 0.5 mm (0.020 in) 
   2. Intake : 37.000 - 37.016 mm (1.4567 - 1.4573 in) 
   3. Exhaust : 32.000 - 32.016 mm (1.2598 - 1.2605 in) 
   • Be sure to ream in circles concentric to the valve guide center. This will enable the valve seat to fit correctly.
3. Heat cylinder head to 110° to 130°C (230° to 266°F) by soaking in heated oil.
4. Provide valve seats cooled well with dry ice. Force fit valve seat into cylinder head.
   CAUTION: Avoid directly touching the cold valve seats.
5. Using a valve seat cutter set or a valve seat grinder, finish the seat to the specified dimensions.
   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 a defective valve seat.
   Fig 2: View Of valve seat cutter

   Courtesy of NISSAN MOTOR CO., U.S.A.

   Grind to obtain the dimensions indicated as shown.

   1. Standard 
   2. D1 dia. : 33.5 mm (1.3189 in) 
   3. D2 dia. : 35.1 - 35.3 mm (1.382 - 1.390 in) 
   4. D3 dia. : 39.0 - 39.2 mm (1.535 - 1.543 in) 
   5. D4 dia. : 28 mm (1.10 in) 
   6. D5 dia. : 29.9 - 30.1 mm (1.177 - 1.185 in) 
   7. D6 dia. : 33.5 - 33.7 mm (1.319 - 1.327 in) 
   Fig 3: Valve Grind Dimensions

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