Subaru IMPREZA 2002 Service Manual page 181

CYLINDER BLOCK
MECHANICAL
4) How to measure the outer diameter of each pis-
ton:
Measure the outer diameter of each piston at the
height shown in the figure. (Thrust direction)
CAUTION:
Measurement should be performed at a temper-
ature of 20°C (68°F).
Piston grade point H:
37.0 mm (1.457 in)
Piston outer diameter:
Standard
A: 99.485
-
99.495 mm
(3.9167
-
3.9171 in)
B: 99.475
-
99.485 mm
(3.9163
-
3.9167 in)
0.25 mm (0.0098 in) oversize
99.725
-
99.735 mm
(3.9262
-
3.9266 in)
0.50 mm (0.0197 in) oversize
99.975
-
99.985 mm
(3.9360
-
3.9364 in)
--
/-
5) Calculate the clearance between cylinder and
piston.
CAUTION:
Measurement should be performed at a temper-
ature of 20°C (68°F).
Cylinder to piston clearance at 20°C (68°F):
0.010
-
0.030 mm (0.0004
-
0.0012 in)
0.050 mm (0.0020 in)
Standard
Limit
6) Boring and honing:
(1)
If the value of taper, out-of-roundness, or
cylinder-to-piston clearance measured exceeds
the specified limit or if there is any damage on
the cylinder wall, rebore it to use an oversize pis-
ton.
CAUTION:
When any of the cylinders needs reboring, all
other cylinders must be bored at the same time,
and use oversize pistons. Do not perform bor-
ing on one cylinder only, nor use an oversize
piston for one cylinder only.
(2) If the cylinder inner diameter exceeds the
limit after boring and honing, replace the crank-
case.
CAUTION:
Immediately after reboring, the cylinder diame-
ter may differ from its real diameter due to tem-
perature rise. Thus, pay attention to this when
measuring the cylinder diameter.
Limit of cylinder enlarging (boring):
3. PISTON AND PISTON PIN
1) Check the pistons and piston pins for damage,
cracks, and wear and the piston ring grooves for
wear and damage. Replace if defective.
2) Measure the piston-to-cylinder clearance at
each cylinder. <Ref. to ME(S0HC)-82, CYLINDER
AND PISTON, INSPECTION, Cylinder Block.> If
any of the clearances is not within specification, re-
place the piston or bore the cylinder to use an over-
size piston.
0.5 mm (0.020 in)
ME(S0HC)-83