Isuzu KB P190. Manual — part 218

ENGINE MECHANICAL 6A – 67

Valve Spring Free Height

Use a vernier caliper to measure the valve spring free height.
If the measured value is less than the specified limit, the valve
spring must be replaced.

Spring Free Height

mm (in)

Standard

Limit

4JA1T (L)

4JA1TC,

4JH1TC

Single spring

48.0 (1.89)

47.1 (1.85)

Valve Spring Squareness

Use a surface plate and a square to measure the valve spring
squareness.
If the measured value exceeds the specified limit, the valve
spring must be replaced.

Spring Squareness

mm (in)

Limit

4JA1T (L)

4JA1TC,

4JH1TC

Single spring

1.7 (0.070)

Valve Spring Tension

Use a spring tester to measure the valve spring tension.

If the measured value is less than the specified limit, the valve
spring must be replaced.

Valve Spring Tension

N (kg/lb)

Compressed

Height

Standard Limit

4JA1T (L)

4JA1TC,

4JH1TC

Single
spring

38.9mm

(1.53in)

296.0

(30.2/66.4)

257.7

(26.3/57.9)

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6A – 68 ENGINE MECHANICAL

ROCKER ARM SHAFT AND ROCKER ARM

Rocker Arm Shaft Run-Out
1. Place the rocker arm shaft on a V-block.

2. Use a dial indicator to measure the rocker arm shaft

central portion run-out.

If the run-out is very slight, correct the rocker arm shaft
run-out with a bench press. The rocker arm must be at cold
condition.

If the measured rocker arm shaft run-out exceeds the
specified limit, the rocker arm shaft must be replaced.

Rocker Arm Shaft Run-Out

mm (in)

Limit

0.3 (0.012)

Rocker Arm Shaft Outside Diameter

Use a micrometer to measure the rocker arm fitting portion
outside diameter.

If the measured value is less than the specified limit, the rocker
arm shaft must be replaced.

Rocker Arm Shaft Outside Diameter

mm (in)

Standard Limit

18.98–19.00 (0.747–0.748)

18.90 (0.744)

Rocker Arm Shaft and Rocker Arm Clearance

1. Use either a vernier caliper or a dial indicator to measure

the rocker arm inside diameter.

Rocker Arm Inside Diameter

mm (in)

Standard Limit

19.010–19.030

(0.748–0.749)

19.100 (0.752)

2. Measure the rocker arm shaft outside diameter.

If the measured value exceeds the specified limit, replace
either the rocker arm or the rocker arm shaft.

Rocker Arm Shaft and Rocker Arm Clearance

mm (in)

Standard Limit

0.01–0.05

(0.0004–0.0020)

0.20 (0.008)

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ENGINE MECHANICAL 6A – 69

3. Check that the rocker arm oil port is free of obstructions.

If necessary, use compressed air to clean the rocker arm
oil port.

Rocker Arm Correction

Inspect the rocker arm valve stem contact surfaces for step
wear (1) and scoring (2).

If the contact surfaces have light step wear or scoring, they
may be honed with an oil stone.

If the step wear or scoring is severe, the rocker arm must be
replaced.

CYLINDER BODY

Cylinder Body Upper Face Warpage

1. Remove the cylinder body dowel.

2. Remove the cylinder liner.

Refer to "Cylinder Liner Replacement".

3. Use a straight edge (1) and a feeler gauge (2) to measure

the four sides and the two diagonals of the cylinder body
upper face.

If the measured values exceeds the limit, the cylinder body
must be replaced.

Cylinder Body Upper Face Warpage

mm (in)

Standard Limit

0.05 (0.002) or less

0.20 (0.008)

Cylinder Body Height (H) (Reference)

mm (in)

Standard

4JA1T(L), 4JA1TC : 244.945-245.055 (9.6435-9.6478)

4JH1TC : 269.945-270.055 (10.6277-10.6320)

4. Reinstall the cylinder liner.

Refer to "Cylinder Liner Replacement".

5. Reinstall the cylinder body dowel.

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6A – 70 ENGINE MECHANICAL

Cylinder Liner Bore Measurement

Use a cylinder indicator to measure the cylinder bore at
measuring point (1) in the thrust (2-2) and axial (3-3) directions
of the crankshaft.

Measuring Point (1): 20 mm (0.79 in)

If the measured value exceeds the specified limit, the cylinder
liner must be replaced.

Cylinder Liner Bore

mm (in)

Standard

Limit

4JA1T(L), 4JA1TC

93.00 (3.6614)

93.08 (3.6646)

4JH1TC

95.40 (3.7559)

95.48 (3.7590)

NOTE:

The inside of the dry type cylinder liner is chrome
plated. It cannot be rebored or honed.

If the inside of the cylinder liner is scored or
scorched, the cylinder liner must be replaced.

Cylinder Liner Projection Inspection

1. Hold a straight edge along the top edge of the cylinder liner

to be measured.

2. Use a feeler gauge to measure each cylinder liner

projection.

Cylinder Liner Projection

mm (in)

Standard

0-0.1 (0-0.004)

The difference in the cylinder liner projection height
between any two adjacent cylinders must not exceed 0.03
mm (0.0012 in).

Cylinder Liner Replacement

Cylinder Liner Removal

1. Insert the cylinder liner remover (1) into the cylinder body

(from the lower side of the cylinder body) until it makes firm
contact with the cylinder liner.

Cylinder Liner Remover : 5-8840-2039-0 (4JA1L/TC)

: 5-8840-2304-0 (4JH1TC)

2. Use a bench press (2) to slowly force the cylinder liner

from the cylinder body.

NOTE:

Take care not to damage the cylinder body upper face
during the cylinder liner removal procedure.

3. Measure the cylinder body upper face warpage.

Refer to "Cylinder Body Upper Face Warpage".

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