Mitsubishi diesel engines - Page 75

ENGINE MAIN PARTS - INSPECTION AND CORRECTION
2 - 30
(a) If any of the crank pins need grinding, grind
all crank pins on the same crankshaft to the
same dimension.
(b) Finish the fillets to a radius of 2 mm (0.08
in.).
3.8 Inspecting the main bearings oil
clearance
(1) Place the main bearings (upper and lower) onto
the cylinder block and the main bearing cap.
Assemble them together and tighten the cap bolts
to the specified torque. Measure the inner
diameter of the main bearings.
(2) Measure the diameter of the mating crank journal.
The difference between the main bearings inner
diameter and the crank journal diameter is the oil
clearance for the main bearings.
Unit: mm (in.)
Nominal
value
Standard
value
Limit
Crank journal
diameter(STD)
φ52
(2.0488)
51.985
to 52.000
(2.0482
to 2.0488)
―
Oil clearance for
main bearings
―
0.030
to 0.077
(0.0012
to 0.003)
0.100
(0.0040)
(3) If the measured oil clearance exceeds the limit,
replace the main bearings. With the new bearings
installed, measure the oil clearance again.
(4) If the measured oil clearance still exceeds the
limit, use the undersize bearings [0.25 mm
(0.0098 in.), 0.50 mm (0.0197 in.), 0.75 mm
(0.0295 in.) U.S.]
Also, grind the crank journal accordingly to the
finished dimension shown below.
Crank journal ground dimensions
Unit: mm (in.)
Finished dimension
0.25 (0.0098)
φ51.75
0
-0.015
(2.0374
0
-0.006
)
0.50 (0.0197)
φ51.50
0
-0.015
(2.0276
0
-0.006
)
Crank
journal
undersize
0.75 (0.0295)
φ51.25
0
-0.015
(2.0177
0
-0.006
)
Finished radius dimension of fillet
Measuring the main bearings inner diameter
Measuring the crank journal diameter
Measuring
location
Measuring
direction
R2.5 mm
(0.098 in.)
Measuring
location
Measuring
direction
Tightening torque
49.0 to 53.9 N
m
(5.0 to 5.5 kgf
m)
[36.2 to 39.8 lbf
ft]