Subaru Impreza 2003 Service Manual page 1078

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)
NOTE:
Measurement should be performed at a tempera-
ture of 20°C (68°F).
Piston grade point H:
40.0 mm (1.57 in)
Piston outer diameter:
Standard
A: 91.985 — 91.995 mm
(3.6214 — 3.6218 in)
B: 91.975 — 91.985 mm
(3.6211 — 3.6214 in)
0.25 mm (0.0098 in) oversize
92.225 — 92.235 mm
(3.6309 — 3.6313 in)
0.50 mm (0.0197 in) oversize
92.475 — 92.485 mm
(3.6407 — 3.6411 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 — 0.030 mm (0.0004 — 0.0012 in)
Limit
0.050 mm (0.0020 in)
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, reboring it to use an oversize
piston.
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.
CYLINDER BLOCK
(2) If the cylinder inner diameter exceeds the
limit after boring and honing, replace the crank-
case.
NOTE:
Immediately after reboring, the cylinder diameter
may differ from its real diameter due to temperature
rise. Thus, pay attention to this when measuring
the cylinder diameter.
Limit of cylinder enlarging (boring):
0.5 mm (0.020 in)
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(H4DOTC)-103, CYLIN-
DER AND PISTON, INSPECTION, Cylinder
Block.> If any of the clearances is not within speci-
fication, replace the piston or bore the cylinder to
use an oversize piston.
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 defective.
Standard clearance between piston pin and
hole in piston:
Standard
Limit
H
ME-00172
ME(H4DOTC)-104
0.004 — 0.008 mm (0.0002 — 0.0003 in)
0.020 mm (0.0008 in)
ME-00173
ME-00174