Subaru Impreza 2003 Service Manual page 298

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:
• 1.6 L and 2.0 L model
40.0 mm (1.575 in)
• 2.5 L model
37.0 mm (1.457 in)
Piston outer diameter:
1.6 L model
Standard
A: 87.885 — 87.895 mm (3.4600 — 3.4604
in)
B: 87.875 — 87.885 mm (3.4596 — 3.4699
in)
0.25 mm (0.0098 in) oversize
88.125 — 88.135 mm (3.4695 — 3.4699 in)
0.50 mm (0.0197 in) oversize
88.375 — 88.385 mm (3.4793 — 3.4797 in)
2.0 L model
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)
2.5 L model
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)
CYLINDER BLOCK
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
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, 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.
(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(H4SO)-85, CYLINDER
AND PISTON, INSPECTION, Cylinder Block.> If
any of the clearances is not to specification, re-
place the piston or bore the cylinder to use an over-
size piston.
H
ME-00172
ME(H4SO)-86
0.010 — 0.030 mm (0.0004 — 0.0012 in)
0.050 mm (0.0020 in)