Mitsubishi 4g63, Service Manual, Page: 45 / 68

CYLINDER HEAD AND VALVES
ENGINE OVERHAUL <4G63-Turbo>
11D-45
VALVE SEAT RECONDITIONING
1. Before reconditioning the valve seat, check the
clearance between the valve guide and valve
stem and, if necessary, replace the valve guide.
2. Resurface the valve seat to the indicated width
and angles.
3. After resurfacing, lap the valve and valve seat
using lapping compound.
VALVE SEAT REPLACEMENT
1. Cut inside of the valve seat to be replaced until its
wall becomes thin enough for removal, then
remove the valve seat.
2. Rebore the valve seat hole in the cylinder head to
a diameter matched to the diameter of the
selected oversize valve seat.
Intake valve seat hole diameters:
0.3 oversize: 35.30
−
35.33 mm
0.6 oversize: 35.60
−
35.63 mm
Exhaust valve seat hole diameters:
0.3 oversize: 33.30
−
33.33 mm
0.6 oversize: 33.60
−
33.63 mm
3. Before fitting the valve seat, cool it in liquid
nitrogen to prevent damage to its hole in the
cylinder head due to interference.
4. Resurface the valve seat. See the VALVE SEAT
RECONDITIONING section.
VALVE GUIDE REPLACEMENT
1. Force out the valve guide toward the cylinder
block using a press.
CAUTION
Do not use a replacement valve guide of the
same size as the removed one.
2. Machine the valve guide hole in the cylinder head
to the size matched to the selected oversize valve
guide.
Valve guide hole diameters
0.05 oversize: 12.05 − 12.07 mm
0.25 oversize: 12.25
−
12.27 mm
0.50 oversize: 12.50
−
12.52 mm
3. Press-fit the valve guide until it remains protruded
above the cylinder head by the amount indicated
in the drawing.
Standard value: 19.2 − 19.8 mm
NOTE: Press the valve guide from above the
cylinder head.
NOTE: The valve guides for the intake valves are
different in length from those for the exhaust
valves (45.5 mm for intake valves; 50.5 mm for
exhaust valves)
4. After installing the valve guide, insert a new valve
in it to check for smooth movement.
AK304983 AC
0.9
‘
1.3 mm
0.9
‘
1.3 mm
65˚
65˚
10˚
10˚
44˚
44˚
AK300719AB
0.5 - 1 mm
0.5 - 1 mm
Cut
AK300720AB
Oversize hole diameter
Valve seat
height
AK400848
19.2 – 19.8 mm
AB