Isuzu engine 4j series. Manual — part 43
6A1 – 40 4JB1/4JB1T/4JB1TC/4JG2 - ENGINE
15. By-pass Hose
16. Cylinder Head Cover
17. Rocker Arm Shaft
•
Loosen the rocker arm shaft bracket bolts a little at a
time in the numerical order shown in the illustration.
NOTE:
Failure to loosen the rocker arm shaft bracket bolts a
little at a time in numerical order will adversely effect
the rocker arm shaft.
18. Push Rod
19. Cylinder Head Assembly
•
Loosen the cylinder head bolts a little at a time in the
numerical order shown in the illustration.
NOTE:
Failure to loosen the cylinder head bolts a little at a
time in numerical order will adversely effect the
cylinder head lower surface.
20. Cylinder Head gasket
•
Remove the cylinder head gasket and dowel.
6A1-40-1.tif
6A1-40-2.tif
6A1-40-3.tif
4JB1/4JB1T/4JB1TC/4JG2 – ENGINE 6A1 – 41
INSTALLATION
20. Cylinder Head 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
1) Use a dial indicator to measure the piston projection
amount.
2) Refer to the illustration for the piston head projection
measuring positions.
All measuring positions should be as close as possible
to the cylinder liner.
3) Measure the points
!"#$
and obtain two
differences
!
-
"
and
#
-
$
on each cylinder.
Calculate the average value of the piston head
projection on each cylinder.
4) Obtain the maximum value in the four cylinders.
5) 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 1.0 mm(0.039 in).
6A1-41-1.tif
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6A1 – 42 4JB1/4JB1T/4JB1TC/4JG2 - ENGINE
4JG2 Cylinder Head Gasket Thickness
mm (in)
Gasket Grade Mark
Piston
Projection
Gasket Thickness
(Reference)
A
0.658 - 0.713
(0.026 - 0.028)
1.60
(0.0630)
B
0.713 - 0.759
(0.028 - 0.030)
1.65
(0.0650)
C
0.759 - 0.814
(0.030 - 0.032)
1.70
(0.0670)
NOTE:
The difference between the highest measured piston
head projection and the lowest measured piston head
projection must not exceed 1.0 mm (0.039 in).
19. Cylinder Head Assembly
1) Install the dowel in cylinder block.
2) Install the cylinder head gasket with top mark up.
3) Clean up cylinder head lower surface and cylinder
body upper surface.
4) Install the cylinder head as softly.
5) Apply engine oil to screw and seat of cylinder head
bolts.
6) Tighten the cylinder head bolts to the specified torque
in three steps following the numerical order shown in
the illustration.
Cylinder Head bolts Torque
N∙m (kg∙m/lb∙ft)
1st Step
2nd Step
3rd Step
49 (5.0/36)
60 - 75°
60 - 75°
18. Push Rod
•
Apply engine oil to push rod and in to the cylinder
head.
17. Rocker Arm shaft
1) Loosen all adjusting screws.
2) Position the rocker arm shaft with the large oil hole
(4ø) facing the front of the engine.
6A1-42-1.tif
6A1-42-2.tif
6A1-42-3.tif
4JB1/4JB1T/4JB1TC/4JG2 – ENGINE 6A1 – 43
3) Tighten the rocker arm shaft bracket bolts to the
specified torque in the numerical order shown in the
illustration.
Rocker Arm Shaft Bracket Bolt Torque
N∙m (kg∙m/lb∙ft)
54 (5.5/40)
•
Valve clearance adjustment.
6A1-43-1.tif
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