Isuzu NHR 4J Series, Workshop Manual

Page: 71 / 406

6A – 4 GENERAL ENGINE MECHANICAL
CAUTION:
Do not attempt to weld the cylinder head. Replace it.
4. Cylinder head deck, intake and exhaust manifold
mating surfaces for flatness.
These surfaces may be re-conditioned by milling
(except cylinder head lower face). If the surfaces are
“out of flat” by more than specification, the surface
should be grinded to within specifications. If more than
limit of specification, it should be replaced.
NOTE:
The cylinder head lower face cannot be reground.
mm (in)
Standard Limit
Cylinder Head
Lower Face
Warpage
0.05 (0.002)
or less
0.20 (0.0079)
Cylinder Head
Height
92 (3.622) 91.55 (3.6043)
5. Water jacket sealing plugs seating surfaces.
6. Use a straight edge and a feeler gauge to measure the
manifold cylinder head lifting face warpage.
Regrind the exhaust manifold cylinder head lifting
surfaces if the measured values are between the
specified limit and the standard.
If the measured values exceed the specified limit, the
manifold must be replaced.
Exhaust Manifold Warpage mm (in)
Standard Limit
0.05 (0.002) or less 0.20 (0.0079)
Hot plug depression (4JG2 only)
1. Clean the cylinder head lower side, taking care not to
damage the hot plug surfaces.
2. Use a straight edge and feeler gauge to measure hot
plug depression in a straight line from the No. 1 hot
plug to the No. 4 hot plug.
If the measured value exceeds the limit, the hot plugs
must be replaced.
Depression Limit mm (in)
0.02 (0.0008)
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