Replacing Valve Seat For Service Parts

WARNING: This page is about a different car, the 2003 Nissan Pathfinder. However, it is still accessible from the selected car via links, so may be relevant.

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.
Ream cylinder head recess 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 the valve guide center.

This will enable valve seat to fit correctly.

Fig 1: Identifying Recess Diameter Of Valve Seat
Courtesy of NISSAN MOTOR CO., U.S.A.
Heat cylinder head to 110 to 130°C (230 to 266°F) by soaking in heated oil.
Press fit valve seat until it seats on the bottom.
CAUTION: Cylinder head contains heat. When working, wear protective equipment to avoid getting burned.
Cut or grind valve seat using suitable tool to the specified dimensions as shown in SDSPRECAUTIONS .
After cutting, lap valve seat with abrasive compound.
Check valve seating condition.
Seat face angle "alpha": 45°

Contacting width "W":

Intake 1.09 - 1.31 mm (0.0429 - 0.0516 in)

Exhaust 1.29 - 1.51 mm (0.0508 - 0.0594 in)

Fig 2: Identifying Valve Fitting Position
Courtesy of NISSAN MOTOR CO., U.S.A.
Use a depth gauge to measure the distance 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 adjust it. If it is longer, replace the valve seat with a new one.
Valve seat resurface limit "L":

Intake 41.07 - 41.67 mm (1.6169 - 1.6405 in)

Exhaust 41.00 - 41.60 mm (1.6142 - 1.6378 in)

Fig 3: Measuring Distance Of Mounting Surface
Courtesy of NISSAN MOTOR CO., U.S.A.