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Service Manual Mitsubishi SQ-Series diesel engines
Version 08/2004
CYLINDER HEADS AND VALVE
MECHANISM
ENGLISH
ENGINE MAIN PARTS
Unit: mm [in.]
S
5. Replacing valve seat
1) Weld a stud to the valve seat. Insert a shaft
through the valve guide from the upper side of
the cylinder head to put its end on the stud, as
shown in the illustration. Then, drive the seat
off from the cylinder head.
Figure 26 Valve contact pattern
Good Bad
NOTE
a Check the valve contact after checking or
replacing the valve guides.
b Do not rotate the valve when holding it
against the seat for checking the contact.
c After refacing or replacing the valve or valve
seat, lap the valve in the seat. (See (8)
Lapping valves.)
Figure 27 Valve contact with valve seat
Valve seat angle
Valve
sinkage
Valve seat width
Valve
margin
Item
Nominal
Value
Assembly
Standard
Repair
Limit
Valve seat
Angle 30°
Width
1.18
[0.05]
1.04 to 1.32
[0.0409 to 0.0520]
1.6
[0.0630]
Valve
sinkage
0.8
[0.03]
0.7 to 0.9
[0.0276 to 0.0354]
1.3
[0.0512]
Valve margin
1.70
[0.07]
1.20
[0.0472]
Figure 28 Replacing valve seat
Weld
Bar
Valve seat
Stud
Valve seat
NOTE
When welding the stud to the valve seat, avoid
contact of any spatter with the machined surface of
the cylinder head.
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