Replacing Valve Seat For Service Parts

WARNING: This page is about a different car, the 2002 Nissan Sentra. However, it is still accessible from the selected car via links, so may be relevant.

Bore out old seat until it collapses. Set machine depth stop so that boring cannot contact the bottom face of seat recess in cylinder head.
Ream cylinder head recess. The reaming bore for the service valve seat are:
Oversize: 0.5 mm (0.020 in)

Intake: 31.500 - 31.516 mm (1.2402-1.2408 in)

Exhaust: 26.500 - 26.516 mm (1.0433-1.0439 in)

Use the valve guide center for reaming to ensure valve seat will have the correct fit.

Fig 1: Determining Recess Diameter
Courtesy of NISSAN MOTOR CO., U.S.A.
Heat cylinder head to 110-130°C (230-266°F).

Fig 2: Heating Cylinder Head In Oil
Courtesy of NISSAN MOTOR CO., U.S.A.
Press fit valve seat until it seats on the bottom.
Cut or grind valve seat using suitable tool to the specified dimensions. Refer to Valve .
After cutting, lap valve seat with abrasive compound.
Check valve seating condition.

Fig 3: Checking Valve Seating Condition
Courtesy of NISSAN MOTOR CO., U.S.A.

Seat face angle "a": 44°53' - 45°07'

Contacting width "W"

Intake: 1.06 -1.34 mm (0.0417 - 0.0528 in)

Exhaust: 1.34 -1.63 mm (0.0528 -0.0642 in)
Use a depth gauge to measure the distance. "L" between the mounting surface of the cylinder head spring seat and the valve stem end. If the distance is shorter than specified, repeat step 5 above to correct it. If the distance is longer, replace the valve seat.
Valve seat resurface limit

Intake: 35.95 - 36.55 mm (1.4154 -1.4390 in)

Exhaust: 35.92 - 36.52 mm (1.4142 - 1.4378 in)

Fig 4: Measuring Distance L
Courtesy of NISSAN MOTOR CO., U.S.A.