Isuzu NHR 4J Series, Workshop Manual

Page: 81 / 406

6A – 14 GENERAL ENGINE MECHANICAL
Valve depression
1. Install the valve (1) to the cylinder head (2).
2. Use a depth gauge or a straight edge with steel rule to
measure the valve depression from the cylinder head
lower surface.
If the measured value exceeds the specified limit, the
valve seat insert must be replaced.
Valve Depression mm (in)
Standard Limit
Inlet 0.73 (0.029) 1.28 (0.050)
4JB1
4JB1T
4JB1TC Exhaust
0.70 (0.028) 1.20 (0.047)
Inlet
4JG2
Exhaust
1.1 (0.043) 1.6 (0.063)
Valve Contact Width
1. Check the valve contact faces for roughness and
unevenness. Make smooth the valve contact surfaces.
2. Measure the valve contact width.
If the measured value exceeds the specified limit, the
valve seat insert must be replaced.
Contact Width mm (in)
Standard Limit
Inlet 1.7 (0.0670) 2.2 (0.0866)
Exhaust 2.0 (0.0788) 2.5 (0.0984)
Valve Seat Insert Replacement
Valve Seat Insert Removal
1. Arc weld the tire inside circumference
!
of the valve
seat insert
"
.
2. Allow the valve seat insert to cool for a few minutes.
This will invite contraction and make removal of the
valve seat insert easier.
3. Use a screwdriver
#
to pry the valve seat insert free.
Take care not to damage the cylinder head
$
.
4. Carefully remove carbon and other foreign material
from the cylinder head insert bore.
Valve Seat Insert Installation
1. Carefully place the attachment
!
(having a smaller
outside diameter than the valve seat insert) on the
valve seat insert
"
.
NOTE:
The smooth side of the attachment must contact the
valve seat insert.
2. Use a bench press
#
to gradually apply pressure to
the attachment and press the valve seat insert into
place.
6A-14-1.tif
6A-14-2.tif
6A-14-3.tif
6A-14-4.tif