Isuzu KB P190. Service 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)
011LX024
014RY00025
011LX026
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)
015LX009
014RY00024
015LX008
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.
014RY00024
012R100001
012RY00009
014RY00023
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".
012RY00010
012LX016
012RY00012
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