Isuzu NHR 4J Series, Workshop Manual

Page: 116 / 406

GENERAL ENGINE MECHANICAL 6A – 49
4JB1 / 4JB1T / 4JB1TC mm (in)
Size Mark Outside Diameter
A 92.985 - 92.994 (3.6608 - 3.6612)
B 92.995 - 93.004 (3.6612 - 3.6616)
C 93.005 - 93.014 (3.6616 - 3.6620)
D 93.015 - 93.024 (3.6620 - 3.6624)
4JG2 mm (in)
Size Mark Outside Diameter
A 95.365 - 95.374 (3.7545 - 3.7549)
B 95.375 - 95.384 (3.7549 - 3.7553)
C 95.385 - 95.394 (3.7553 - 3.7557)
D 95.395 - 95.404 (3.7557 - 3.7561)
The grading position for piston outside diameter is
represented by the ‘G’ as shown in Figure.
Measure the cylinder bore inside diameter (refer to
“inspection of the cylinder Block” in this Section).
If the piston clearance does not conform to the specified
valve, the piston and/or cylinder liners must be replaced.
Piston Clearance
mm (in)
4JB1 / 4JB1T / 4JB1TC 0.061 (0.0024)
4JG2 0.066 (0.0026)
Selection method of piston grade for service parts.
If you find piston grade A from size mark or piston outside
diameter measurement result, you will select AX for
service piston grade.
The stamped piston grade on the head of piston for
service parts.
Service piston grade
Piston Size Mark Service Parts Grade
A AX
B AX
C CX
D CX
Service piston diameter mm (in)
Piston Grade 4JB1 / 4JB1T / 4JB1TC
AX 92.989 - 93.004 (3.6610 - 3.6616)
CX 93.005 - 93.020 (3.6616 - 3.6622)
Piston Grade 4JG2
AX 95.369 - 95.384 (3.7547 - 3.7553)
CX 95.385 - 95.400 (3.7553 - 3.7559)
6A-49-1.tif