Isuzu N-Series. Manual - part 563

GENERAL ENGINE MECHANICAL 6A-9

• Apply a wrench as illustrated and tighten the

holder nut to the specified torque using a spe-
cial tool.

Caution:

• After tightening the holder nut, make sure that the

drilled hole makes 

±5° or smaller with the cylinder

head-side positioning boss.

• When mounting leak off pipe, injection nozzle and

pipe, clean then with air so that dust may not enter.

Tighten:
Nozzle fixing to 64 N

⋅m (6.5 kg⋅m/47 lb⋅ft)

Wrench: Nozzle holder 5-8840-0259-0

9. Thermostat Housing Assembly

Tighten:
Thermostat housing assembly fixing bolt to 19 N

⋅m (1.9

kg

⋅m/14 lb⋅ft)

Legend

1. Glow plug
2. Positioning boss

N6A3072E

N6A3073E

6A-10 GENERAL ENGINE MECHANICAL

VALVE SPRING, VALVE GUIDE OIL SEAL, VALVE GUIDE, PUSH ROD

Component

Disassembly

1. Rocker Arm Assembly
2. Split Collar

Using special Tool, compress valve spring
Valve spring compressor: 9-8523-1423-0 (J-
29760)

3. Valve Spring
4. Valve

Legend

1. Rock arm assembly

4. Valve

2. Split collar

5. Valve guide oil seal

3. Valve spring

6. Valve guide

N6A3074E

N6A3075E

GENERAL ENGINE MECHANICAL 6A-11

5. Valve Guide Oil Seal
6. Valve Guide

Valve Guide Replacer: 9-8523-1212-0

Inspection and Repair

Make the necessary adjustments, repairs, and part re-
placements if excessive wear or damage is discovered
during inspection.

Valve spring

Caution:
Visually inspect the valve springs and replace them if
damage or abnormal wear is evident.

1. Free height

• Measure the free height of the springs. The

springs must be replaced if the height is below
the specified limit.

2. Squareness

• Measure the valve spring squareness with a

steel square.

• Replace the valve springs if the measured val-

ue exceeds the specified limit.

3. Spring tension

• Use spring tester to compress the springs to

the installed height. Measure the compressed
spring tension.
Replace the springs if the measured tension is
below the specified limit.

Valve Guide

Caution:
Taking care not to damage the valve seat contact sur-
face, when removing carbon adhering to the valve head.
Carefully inspect the valve stem for scratching or abnor-
mal wear. If these conditions are present, the valve and
the valve guide must be replaced as a set.

Free Height

mm (in)

Standard

Limit

48.0 (1.891)

47.100 (1.8560)

Limit

mm (in)

1.7 (0.067)

N6A3076E

Tension

N (kg/lb)

At installed height 
38.9 mm (1.5 in)

Standard

Limit

296.2 (30.2/

66.6)

257.9 (26.3/

57.9)

N6A3077E

N6A3078E

6A-12 GENERAL ENGINE MECHANICAL

1. Valve Guide Clearance

• Measure the valve stem diameter with a mi-

crometer.
If the valve stem diameter is less than the spec-
ified limit, the valve and the valve guide must be
replaced as a set.

• Measure the inside diameter of the valve guide

with a micrometer.

• Subtract the measured outer diameter of the

valve stem from the measured inner diameter
of the valve guide. If the valve exceeds of the
valve guide.
If the valve exceeds the specified limit, the
valve and the valve guide must be replaced as
a set.

Valve Guide Replacement

1. Using special tool, drive out the valve guide from

the combustion chamber side.

Valve guide replacer: 9-8523-1212-0

2. Apply engine oil to the outside of the valve guide.

Using special tool, drive in a new valve guide from
cylinder head upper face side, and check the valve
guide height.

Valve guide replacer: 9-8523-1212-0

Notice:
If the valve guide has been removed, both the valve and
the valve guide must be replaced as a set.

mm (in)

Standard

Limit

Diameter of
Valve stem

Inlet

7.946 — 7.961 

(0.3128 — 

0.3134)

7.880 

(0.310.2)

Exhaust

7.921 — 7.936 

(0.3118 — 

0.3124)

7.850 

(0.3091)

Valve Guide Clearance

mm (in)

Standard

Limit

Inlet clearance

0.039 — 0.069 

(0.0015 — 

0.0027)

0.200 

(0.0079)

Exhaust clearance

0.064 — 0.096 

(0.0025 — 

0.0038)

0.250 

(0.0098)

N6A3079E

Height

mm (in)

13 (0.51)

N6A3080E

N6A3067E