Isuzu NHR 4J Series, Workshop Manual

Page: 133 / 406

6A – 66 GENERAL ENGINE MECHANICAL
2. Oil Pan Assembly
Above works refer to “OIL PUMP” Section in this
manual.
1. Cylinder Head Assembly and Gasket
!
Cylinder head gasket is determined by the piston
head projection from the cylinder body upper
surface, in order to improve engine performance.
Three types of gasket are provided by the
difference of thickness. Select the adequate one
out of three grades of gasket, according to the
following procedure.
Before measurement, clear off carbon from the
piston head and cylinder body surface and also
clean the place where a gasket was installed.
Piston Head Projection Measurement Point
"
Use a dial indicator to measure the piston
projection amount.
#
Refer to the illustration for the piston head
projection measuring positions.
All measuring positions should be as close as
possible to the cylinder liner.
$
Measure the points
! " # $
and obtain two
difference
!
-
"
and
#
-
$
on each cylinder.
Calculate the average value of the piston head
projection on each cylinder.
%
Obtain the maximum value in the four cylinders.
&
Determine the gasket grade required to the
maximum value described above in accordance
with the following table.
4JB1 / 4JB1T / 4JB1TC
Cylinder Head Gasket Thickness
mm (in)
Gasket Grade
Mark
Piston
Projection
Gasket
Thickness
(Reference)
A
0.758-0.813
(0.030-0.032)
1.60 (0.0630)
B
0.813-0.859
(0.032-0.034)
1.65 (0.0650)
C
0.859-0.914
(0.034-0.036)
1.70(0.0670)
NOTE:
The difference between the highest measured piston
head projection and the lowest measured piston head
projection must not exceed 1.0mm (0.039 in).
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