Isuzu N-Series. Manual - part 577

GENERAL ENGINE MECHANICAL 6A-65

16) Position the bearing cap front mark so that it is

facing the front of the engine.

17) Install the connecting rod bearing caps.

Align the bearing cap cylinder number marks
and the connecting rod cylinder number marks.

18) Apply a coat of engine oil to the threads and

setting faces of each connecting rod cap bolt.

19) Tighten the connecting rod bearing cap bolts to

the specified torque in two steps using the An-
gular Tightening Method.

Tighten:
Connecting Rod Bearing Cap Bolt to

• 4JB1-TC,  4JH1-TC

1st Step: 29 N

⋅m (3.0 kg⋅m/22 lb⋅ft)

2nd Step: 45

° — 60°

• 4JB1: 83 N

⋅m (8.5 kg⋅m/61 lb⋅ft)

Notice:
Check to see that the crankshaft turns smoothly by ro-
tating it manually.

10. Piston Cooling Oil Pipe

1) Fix the oil jet pipes with knock pins on the cylin-

der block.

2) Install the oil pipe for piston cooling in the cylin-

der block, tightening a relief valve (1) and four
joint bolts (2) to the specified torque.

Tighten:

• Oil pipe fixing bolts to

M8: 19 N

⋅m (1.9 kg⋅m/14 lb⋅ft)

M6: 8 N

⋅m (0.8 kg⋅m/69 lb⋅in)

• Relief valve fixing bolt to 29 N

⋅m (3 kg⋅m/22 lb⋅ft)

Caution:
After installed the piston assembly. Check and see that
there is appropriate clearance between pistons and oil
jet pipes by rotating crankshaft slowly.

Legend

1. Front mark

N6A3210E

N6A3211E

N6A3212E

N6A3213E

6A-66 GENERAL ENGINE MECHANICAL

11. Oil Pump Assembly

Above works refer to “OIL PUMP” Section in this
manual.

12. Timing Pulley Housing
13. Timing Gear Housing
14. Front Oil Seal (Belt Drive Model)
15. Timing Belt and Pulley

1) Camshaft Timing Pulley
2) Timing Belt
3) Flange: Camshaft Pulley
4) Timing Pulley Lower Cover
5) Timing Pulley Upper Cover
6) Crankshaft Damper Pulley

16. Timing Gear (Gear Drive Model)

1) Crankshaft Gear
2) Crankshaft Timing Gear
3) Idle Gear
4) Idler Gear “B” and Shaft
5) Injection Pump
6) Timing Gear Oil Pipe
7) Timing Gear Case Cover
8) Crankshaft Damper Pulley
9) Cooling Fan Assembly
10) AC Generator, Power Steering Pump Drive

Belt

11) Fan Shroud

Above works refer to “CRANKSHAFT” Section
in this manual.

17. Oil Pan Assembly

Above works refer to “OIL PUMP” Section in this
manual.

18. Cylinder Head Assembly and Gasket

1) Cylinder head gasket is determined by the pis-

ton head projection from the cylinder body up-
per surface, in order to improve engine
performance.
Three types of gasket are provided by the dif-
ference 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

2) Use a dial indicator to measure the piston pro-

jection amount.

3) Refer to the illustration for the piston head pro-

jection measuring positions.
All measuring positions should be as close as
possible to the cylinder liner.

4) Measure the points (1) (2) (3) (4) and obtain

two difference (1) — (2) and (3) — (4) on each
cylinder.
Calculate the average value of the piston head
projection on each cylinder.

5) Obtain the maximum value in the four cylinders.
6) Determine the gasket grade required to the

maximum value described above in accor-
dance with the following table.

4JB1 / 4JB1-TC
Cylinder Head Gasket Thickness

N6A3214E

N6A3215E

GENERAL ENGINE MECHANICAL 6A-67

4JB1

Notice:
The difference between the highest measured piston
head projection and the lowest measured piston head
projection must not exceed 1.0mm (0.039 in).

4JG2 Cylinder Head Gasket Thickness

4JG2

Legend

1. Gasket grade mark
2. Piston projection
3. Gasket thickness (Reference)

N6A3690E

N6A3216E

Legend

1. Gasket mark
2. Average piston projection
3. Gasket thickness

Legend

1. Gasket mark

N6A3693E

N6A3217E

6A-68 GENERAL ENGINE MECHANICAL

4JH1-TC
Cylinder Head Gasket Thickness

4JH1

Notice:
The difference between the highest measured piston
head projection and the lowest measured piston head
projection must not exceed 1.0mm (0.039 in).

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 molybdenum disulfide grease to screw and

seat of cylinder head bolts.

6. Tighten the cylinder head bolts to the specific

torque in three step following the numerical and
shown in the illustration.

Tighten:
Cylinder Head Bolts to

• 1st Step: 49 N

⋅m (5 kg⋅m/36 lb⋅ft)

• 2rd Step: 60

° — 75°

• 3rd Step: 60

° — 75°

Push Rod

• Apply engine oil to push rod and into the cylinder

head.

Rocker Arm Shaft Assembly

1. Loosen all adjusting screws.
2. Position the rocker arm shaft with the large oil hole

(4

φ) facing the front of the engine.

Legend

1. Gasket grade mark
2. Piston projection
3. Gasket thickness (Reference)

Legend

1. Grade mark

N6A3691E

N6A3218E

N6A3219E

N6A3119E