Mitsubishi diesel engines - Measuring the Cylinder Bore; Measuring the Cylinder Block Top Face for Distortion

ENGINE MAIN PARTS - INSPECTION AND CORRECTION
2 - 32
3.12 Measuring the cylinder bore
Using a cylinder gauge, measure the cylinder
bore and cylindricality. If any of the cylinders
exceeds the limit, bore all cylinders of the same
engine and replace the pistons and the piston
rings with oversize parts.
Measure at 3 locations as shown in the fig., each
in directions A and B.
Unit: mm (in.)
Pistons and piston
rings available
Cylinder bore
Size Code
Standard
value
Limit
STD STD
φ78
+0.03
0
(3.07
+0.012
0
)
0.25 OS 25
φ78.25
+0.03
0
(3.08
+0.012
0
)
0.50 OS 50
φ78.50
+0.03
0
(3.09
+0.012
0
)
Standard
value
+0.2
(0.0080)
Cylinder bore out of
cylindricality
±0.01
(0.0004)
max
―
3.13 Measuring the cylinder block top face for
distortion
Using a straight edge across the top face of the
cylinder block and a thickness gauge, measure
for any distortion.
If the measured distortion exceeds the limit,
correct by grinding the top face.
Unit: mm (in.)
Standard
value
Limit
Cylinder block top face
distortion
0.05 (0.002)
max
0.10 (0.004)
The combined grinding limit for the cylinder
block top face and the mating cylinder head
bottom face is 0.2 mm (0.008 in.).
Measuring the cylinder bore
Measuring the cylinder block top face for
distortion
A
B
Measuring
location
Measuring
direction
Measuring location,
Measuring direction