Valve seat replacement and treatment (Mitsubishi Colt 5)

1. If it is necessary to remove the valve seat, first machine the inside of the seat with a cutter to make it easier to remove (Figure 4.20).

Figure 4.20. To make removing the saddle easier, first cut it with a milling cutter

2. Drill the valve seat hole in the cylinder head to the next repair size (Figure 4.21).

Figure 4.21. Drill the valve seat hole in the cylinder head to the next repair size

Repair diameter for inlet valve seat:

0.3 mm:

SOHC-31.80-31.83 mm
DOHC - 34.30-34.33 mm

0.6 mm:

SOHC-32.10-32.13 mm
DOHC - 34.60-34.63 mm

Repair diameter for exhaust valve seat:

0.3 mm:

SOHC - 29.30-29.32 mm
DOHC - 30.80-30 83 mm

0.6 mm:

SOHC - 29.60-29.62 mm
DOHC-31.10-31.13 mm

3. Before installing the valve seat, heat the cylinder head to 250° or cool the valve seat in liquid nitrogen to avoid deformation of the cylinder head bore.

4. Machine the valve seat to the required dimensions, namely the required angles and width.

5. Before you begin resurfacing the valve seat, check the clearance between the valve guide and the valve. If necessary, replace the guide or valve.

6. Use a special tool or cutter to machine the valve seat so that the angles and width of the valve seat correspond to the specified dimensions. The valve seat angles are shown in Figure 4.22.