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.

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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).

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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.

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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.

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