Mitsubishi 4DQ3 Service Manual page 5

Valve guides and valve sea ts
(1) Check each valve for carboning, burning, wear or
other defect on head; also check cap end and stem
for cracks. Replace the valve if damaged.
(2)
Check each valve guide for wear. Remember, the
guide wears down more rapidly at its both ends
than at any other parts. Measure the inside dia·
meter of the guide at its ends and at its middle
part in two directions. Measure the outside dia·
meter of each valve stem. If the measureme nt
exceeds the repair limit in Table below, replace
the valve guide.
(3) Valve face and valve seat
Check valve face and valve seat for wear and
contact. If valve face is found excessively worn,
reface it by using a valve refacer. To reface the
valve, proceed as follows:
Item
Angle
Sinka ge
Valve
seat
Width
Valve margin
Specifications
Nominal
Standard
value
°
30
±0.2
0.8 ( 0.031)
(±0.008}
±0.14
1.4 (0.055)
(±0.0055)
1.7 (0.067)
_J
)
�:
Wear on valve guide
Specifications
Item
Clearance
In ta ke
{0.00217-0.00335}
of valve
stem in
Exhaust
valve guide (0.00276-0. 00413 )
Valve guide
length out-
side hole
Intake
Valve stem
diameter
Exhaust
Repair
limit
13
(0. 051 )
�
1.6
(0. 063)
Va lv e s ee t
angle
Reface up to
1.2
(0.047)
1 .
. '
:�
Unit: mm (in.)
Repair
Standard
limit
0.055-0.085 0.15
(0 .0 05 9 )
0. 20
0.070-0.105
(0 . 007 9 )
±
18 0.3
(0.70 9 ± 0.012)
g - 0.045
-0.10
-0.060
(- 0.003 9)
7 7 }
(0 315 -0 .001
·
-0.00236
g -0.060
-0.080
-0.15
( - 0.00 59 )
(0 3 15 -0.00236 )
-0.00315
Unit: mm (in.)
� n
Service limit
n
. l
5
i- Bore diam
!
"'
Fac e•
e
� �
V
i
1 Va l ve sin k ag e
j Counterbore V alve margin