Isuzu NHR 4J Series, Workshop Manual

Page: 78 / 406

GENERAL ENGINE MECHANICAL 6A – 11
INSPECTION AND REPAIR
Make the necessary adjustments, repairs, and part
replacements 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.
Free Height mm (in)
Standard Limit
48.0 (1.891) 47.100 (1.8560)
2. Squareness
• Measure the valve spring squareness with a steel
square.
• Replace the valve springs if the measured value
exceeds the specified limit.
Limit mm (in)
1.7 (0.067)
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.
Tension N (kg/lb)
Standard Limit
At installed height
38.9 mm (1.5 in)
296.2 (30.2/66.6) 257.9 (26.3/57.9)
Valve Guide
CAUTION:
Taking care not to damage the valve seat contact
surface, when removing carbon adhering to the valve
head.
Carefully inspect the valve stem for scratching or
abnormal wear. If these conditions are present, the
valve and the valve guide must be replaced as a set.
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