Isuzu N-Series. Manual - part 325

6A-42 ENGINE MECHANICAL

Clearance Measurements (With Plastigage)
Crankshaft Journal and Bearing Clearance

1. Clean the cylinder body and crankcase, the journal

bearing fitting surface, and the journal bearings.

2. Install the bearings to the cylinder body and crank-

case.

3. Carefully place the crankshaft on the bearings.
4. Rotate the crankshaft approximately 30 degrees to

seat the bearing.

5. Place the Plastigage (arrow) over the crankshaft

journal across the full width of the bearing.

6. Install the crankcase to the cylinder body.

Connecting Rod Bearing Combination

mm (in)

Engine Model

Connecting Rod Big End

Crankpin

Connecting 

Rod Bearing

Oil Clearance

4HF1 4HF1-2 

4HG1 4HG1-T

Grade Mark

Diameter

Diameter

Color Code

A

69.985 — 69.992 

(2.7553 — 2.7556)

65.902 — 65.992 

(2.5946 — 2.5954)

Green

0.036 — 0.077 

(0.0014 — 0.0030)

B

69.993 — 70.000 

(2.7556 — 2.7559)

65.902 — 65.922 

(2.5946 — 2.5954)

Yellow

0.036 — 0.070 

(0.0014 - 0.0030)

4HE1-TC

A

77.985 — 77.992 

(3.0703 — 3.0705)

72.902 — 72.922 

(2.8702 — 2.8709)

Green

0.037 — 0.077 

(0.0015 — 0.0030)

B

77.993 — 78.000 

(3.0706 — 3.0709)

Yellow

N6A0214E

N6A0215E

N6A0216E

ENGINE MECHANICAL 6A-43

7. Tighten the crankcase to the specified torque in the

numerical order shown in the illustration.

Tighten:
Crankcase bolt (M14: (1) — (10)) to

• 1st step: 98 N

⋅m (10 kg⋅m / 72 lb⋅ft)

• 2nd step: 132 N

⋅m (13.5 kg⋅m / 98 lb⋅ft)

• 3rd step: 30 — 60

°

Tighten:
Crankcase bolt (M10: (1) — (17)) to 3.9

±0.7 N⋅m (28±5

kg

⋅m / 38±7 lb⋅ft)

Do not allow the crankshaft to turn during bearing
cap installation and tightening.

8. Remove the bearing beam and the crankcase with

bearings.

9. Compare the width of the Plastigage attached to ei-

ther the crankshaft or the bearing with the scale
printed on the Plastigage container.

10. If the measured value exceeds the limit, perform

the following additional steps.

N6A0217E

N6A1415E

Crankshaft Journal and Bearing 
Clearance

mm (in)

Standard

Limit

No.1, 2, 4 

and 5 Journal

0.037 — 0.072 

(0.0015 — 

0.0028)

0.11 (0.0043)

No.3 Journal

0.051 — 0.086 

(0.0020 — 

0.0034)

0.11 (0.0043)

N6A0208E

N6A0219E

6A-44 ENGINE MECHANICAL

• Use a micrometer to measure the crankshaft

outside diameter.

• Use an inside dial indicator to measure the

bearing inside diameter.
If the crankshaft journal and bearing clearance
exceeds the limit, the crankshaft and/or the
bearing must be reground (Except 4HE1-TC)
or replaced.

11. Remove the crankshaft and bearings.
Crankpin and Connecting Rod Bearing Clearance

1. Clean the crankshaft, the connecting rod, the bear-

ing cap, and the bearings.

2. Install the bearing to the connecting rod and the

bearing cap.
Do not allow the crankshaft to move when installing
the bearing cap.

3. Prevent the connecting rod from moving.
4. Attach the Plastigate to the crankpin.

Apply engine oil to the Plastigate to keep it from
falling.

5. Apply a coat of molybdenum disulfide grease to the

bearing cap bolt threads and setting faces.

6. Install the bearing cap and tighten it to the specified

torque.
Do not allow the connecting rod to move when in-
stalling and tightening the bearing cap.

Tighten:
Connecting rod bearing cap bolt to

• 1st step: 39 N

⋅m (4.0 kg⋅m / 29 lb⋅ft)

• 2nd step: 60

°

• 3rd step: 30

°

7. Remove the bearing cap.

8. Compare the width of the Plastigate attached to ei-

ther the crankshaft or the bearing against the scale
printed on the Plastigage container.

9. If the measured value exceeds the specified limit,

perform the following additional steps.

• Use a micrometer to measure the crankpin out-

side diameter.

• Use an inside dial indicator to measure the

bearing inside diameter.
If the clearance between the crankpin and the
bearing exceeds the specified limit, the crank-
shaft and / or the bearing must be reground (ex-
cept 4HE1-TC) or replaced.

Crankshaft Regrinding (Except 4HE1-TC)
To ensure crankshaft reliability, pay close attention to
the following items during and after the crankshaft jour-
nal and crankpin regrinding procedure.

Undersized Crankshaft 
Journal Bearing Avail-
ability (Except 4HE1-TC)

mm (in)

0.25 (0.01)

0.50 (0.02)

N6A0220E

Crankpin and Connecting 
Rod Bearing Clearance

mm (in)

Standard

Limit

0.036 — 0.077 (0.0014 — 

0.0030)

0.10 (0.004)

Undersized Connecting 
Rod Bearing Availability 
(Except 4HE1-TC)

mm (in)

0.25 (0.01)

0.50 (0.02)

Undersized Bearing 
Availability

mm (in)

0.25 (0.01)

0.50 (0.02)

N6A0221E

ENGINE MECHANICAL 6A-45

Crankshaft Regrinding Procedure (Except 4HE1-TC)

1. Regrind the crankshaft journals and the crankpins.
2. Fillet the crankshaft journals and the crankpin radi-

uses to a minimum of R 4.8

±0.2 mm

(0.189

±0.0078 in).

There must be no stepping around the fillet area.

3. Finish the crankshaft journals, the crankpins, and

the oil port corners to a smooth surface having a
chamfer radius of 1 mm (0.04 in).

4. Check the crankshaft journal and crankpin clear-

ance.
Refer to the “Crankshaft Journal and Bearing
Clearance” and “Crankpin and Connecting Rod
Bearing Clearance”.

5. Check the crankshaft run-out.

Refer to the “Crankshaft Run-Out”.

Caution:
The crankshaft for 4HE1-TC is applied soft nitrided sur-
face (Taftriding). Therefore, the crankshaft for 4HE1-TC
not could be ground.

Inspection Procedure for Soft Nitrided (Taftriding)
Crankshaft (For 4HE1-TC)

1. Inspect the crankshaft following points.

• Excessive wear and damage on the surface of

crankshaft journals.

• Excessive wear and damage on the surface of

crankpin.

• Excessive wear and damage on the oil seal fit-

ting surface.

• Inspect the oil ports foe obstructions.

2. Inspect the crankshaft soft nitrided surface (Taftrid-

ing). The soft nitrided crankshaft has been applied
to increase crankshaft strength.
Because of this, it is not possible to regrind the
crankshaft surfaces.
1) Inspection conditions.

• Remove the oil and other material on the

crankshaft inspection area.

• The portion to be tested must be held hori-

zontally so as not let the test solution flow.

• Test liquid should not be applied to the ap-

proximately 10 mm (0.39 in) area around the
oil port (2).

2) Inspection method

• Use an organic cleaner to thoroughly clean

the crankshaft. There must be no traces of
oil the surfaces to be inspected.

• Prepare a 5 — 10 percent solution of ammo-

nium cupric chloride (dissolved in distilled
water).

• Use a syringe to apply the solution (1) to the

surface to be inspected. Hold the surface to
be inspected perfectly horizontal to prevent
the solution from running.

3) Judgement

• Wait for thirty to forty seconds. If there is no

discoloration after thirty to forty seconds, the
crankshaft is usable. If discoloration ap-
pears (the surface being tested will become
the color copper), the crankshaft must be re-
placed.

• Steam clean the crankshaft surface immedi-

ately after completing the inspection.

Notice:
The ammonium cupric chloride solution is highly corro-
sive. Because of this, it is imperative that the surfaces
being inspected be cleaned immediately after complet-
ing the inspection.

Crankshaft Journal and Crankpin 
Grinding Limit (Reference)

mm (in)

Journal

No.1, 2, 4, 5

81.405 (3.2049)

No.3

81.390 (3.2043)

Crankpin

65.402 (2.5749)

Crankshaft Journal and Crankpin Roughness

0.4 

µm or less

N6A0222E