Subaru IMPREZA GD 2007 Series Manual page 2486

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4) Piston outer diameter measurement
Measure the outer diameter of each piston at the
height as shown in the figure. (Thrust direction)
NOTE:
Measurement should be performed at a tempera-
ture of 20°C (68°F).
Piston grade point H:
38.2 mm (1.50 in)
Piston outer diameter:
Standard
A: 99.505 — 99.515 mm (3.9175 — 3.9179
in)
B: 99.495 — 99.505 mm (3.9171 — 3.9175
in)
0.25 mm (0.0098 in) oversize
99.745 — 99.765 mm (3.9270 — 3.9278 in)
0.50 mm (0.0197 in) oversize
99.995 — 100.015 mm (3.9368 — 3.9376 in)
5) Calculate the clearance between cylinder and
piston.
NOTE:
Measurement should be performed at a tempera-
ture of 20°C (68°F).
Cylinder to piston clearance at 20°C (68°F):
Standard
–0.010 — 0.010 mm (–0.0004 — 0.0004 in)
Limit
0.030 mm (0.0012 in)
6) Boring and honing
(1) If any of the value of taper, out-of-round-
ness, or cylinder-to-piston clearance exceeds
the specified limit or if there is any damage on
the cylinder wall, rebore it for replacement with
an oversize piston.
CAUTION:
• When any of the cylinders needs reboring,
other cylinders must be bored at the same time,
and replaced with oversize pistons.
• Do not perform boring on one cylinder only.
Do not replace only a single cylinder for an
oversize piston.
Cylinder Block
(2) If the cylinder inner diameter exceeds the
limit after boring and honing, replace the cylin-
der block.
NOTE:
Immediately after reboring, the cylinder diameter
may differ from its real diameter due to temperature
rise. Thus, when measuring the cylinder diameter,
wait until it has cooled to room temperature.
Cylinder inner diameter boring limit (diameter):
To 100.005 mm (3.937 in)
3. PISTON AND PISTON PIN
1) Check the piston and piston pin for breaks,
cracks or wear. Replace if faulty.
2) Check the piston ring groove for wear or dam-
age. Replace if faulty.
3) Make sure that the piston pin can be inserted
into the piston pin hole with a thumb at 20°C (68°F).
Replace if faulty.
Standard clearance between piston pin and
hole in piston:
Standard
0.004 — 0.008 mm (0.0002 — 0.0003 in)
Limit
0.020 mm (0.0008 in)
H
ME-00172
ME(H4DOTC)-85
MECHANICAL
ME-00173
ME-00174