Subaru Legacy (2005 year). Manual - part 74

ME(H4SO 2.0)-79

MECHANICAL

Cylinder Block

2) How to measure the inner diameter of each cyl-
inder
Measure the inner diameter of each cylinder in both
the thrust and piston pin directions at the heights as
shown in the figure, using a cylinder bore gauge.

NOTE:
Measurement should be performed at a tempera-
ture of 20

°C (68°F).

Cylindricality:

Standard

0.015 mm (0.0006 in)

Out-of-roundness:

Standard

0.010 mm (0.0004 in)

3) When the piston is to be replaced due to general
or cylinder wear, determine a suitable sized piston
by measuring the piston clearance.

4) How to measure the outer diameter of each cyl-
inder:
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:

2.0 L model

40.0 mm (1.575 in)

2.5 L model

37.0 mm (1.457 in)

Standard:

2.0 L model

A: 92.005 — 92.015 mm (3.6222 — 3.6226 in)
B: 91.995 — 92.005 mm (3.6219 — 3.6222 in)

2.5 L model

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

2.0 L model

92.245 — 92.265 mm (3.6317 — 3.6325 in)

2.5 L model

99.745 — 99.765 mm (3.9270 — 3.9278 in)

0.50 mm (0.0197 in) oversize

2.0 L model

92.495 — 92.515 mm (3.6415 — 3.6423 in)

2.5 L model

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 (

−

0.00039 — 0.00039 in)

(A) Piston pin direction

(B) Thrust direction

H1 10 mm (0.39 in)

H2 45 mm (1.77 in)

H3 80 mm (3.15 in)

H4 115 mm (4.53 in)

ME-00171

(A)

(B)

H2

H1

H3

H4

ME-00172

H

ME(H4SO 2.0)-80

MECHANICAL

Cylinder Block

6) Boring and honing

(1) If any of the measured value of taper, out-of-
roundness or cylinder-to-piston clearance ex-
ceeds the standard 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 cylin-
der block.

Cylinder inner diameter limit:

2.0 L model

92.515 mm (3.6423 in)

2.5 L model

100.015 mm (3.9376 in)

NOTE:
Immediately after reboring, the cylinder diameter
may differ from its real diameter due to temperature
rise. Thus, pay attention when measuring the cylin-
der diameter.

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 2.0)-78, CYLIN-
DER AND PISTON, INSPECTION, Cylinder
Block.> If any of the clearances is not within stan-
dard, 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.

Clearance between piston hole and piston pin:

Standard

0.004 — 0.008 mm (0.0002 — 0.0003 in)

4) Check the snap ring installation groove (A) on
the piston for burr. If necessary, remove burr from
the groove so that the piston pin can lightly move.

5) Check the piston pin snap ring for distortion,
cracks and wear.

ME-00173

ME-00174

ME-00175

(A)

ME(H4SO 2.0)-81

MECHANICAL

Cylinder Block

4. PISTON RING

1) If the piston ring is broken, damaged or worn, or
if its tension is insufficient, or when the piston is re-
placed, replace the piston ring with a new one of
the same size as the piston.

CAUTION:
• Marks are displayed on the end of top and
second rings. When installing the rings to the
piston, face these marks upward.
• Oil ring consists of the upper rail, expander
and lower rail. Be careful about the direction of
rail when installing the oil ring to piston. 

2) Clean the piston ring groove and piston ring.

3) Squarely place the piston ring and oil ring in cyl-
inder, and measure the piston ring gap with a thick-
ness gauge.

4) Measure the clearance between piston ring and
piston ring groove using thickness gauge.

(A) Upper rail

(B) Expander

(C) Lower rail

ME-02480

(A)

(B)

(C)

(A)

(B)

(C)

Standard

mm (in)

Piston ring 
gap

Top ring

0.20 — 0.35

(0.0079 — 0.0138)

Second 
ring

2.0 L

0.40 — 0.50

(0.0157 — 0.0197)

2.5 L

0.37 — 0.52

(0.0146 — 0.0204)

Oil ring rail

0.20 — 0.50

(0.0079 — 0.0197)

Standard

mm (in)

Clearance 
between pis-
ton ring and 
piston ring 
groove

Top ring

0.040 — 0.080

(0.0016 — 0.0031) 

Second ring

0.030 — 0.070

(0.0012 — 0.0028) 

ME-00177

ME-00178

ME(H4SO 2.0)-82

MECHANICAL

Cylinder Block

5. CONNECTING ROD

1) Replace the connecting rod, if the large or small
end thrust surface is damaged.
2) Check for bend or twist using a connecting rod
aligner. Replace the connecting rod if the bend or
twist exceeds the limit.

Limit of bend or twist per 100 mm (3.94 in) in 
length:

0.10 mm (0.0039 in)

3) Install the connecting rod fitted with bearing to
crankshaft and measure the thrust clearance. If
thrust clearance exceeds the standard, replace the
connecting rod.

Connecting rod thrust clearance:

Standard

0.070 — 0.330 mm (0.0028 — 0.0130 in)

4) Inspect the connecting rod bearing for scar,
peeling, seizure, melting, wear, etc.

5) Measure the oil clearance on individual connect-
ing rod bearings by means of plastigauge. If any oil
clearance is not within the standard, replace the
defective bearing with a new one of standard size
or undersize as necessary. (See the table below.)

Connecting rod oil clearance:

Standard

0.016 — 0.044 mm (0.00063 — 0.0017 in)

6) Inspect the bushing at connecting rod small end,
and replace if worn or damaged. Also measure the
piston pin clearance at the connecting rod small
end.

Clearance between piston pin and bushing:

Standard

0 — 0.022 mm (0 — 0.0009 in)

(A) Thickness gauge

(B) Connecting rod

( A )

( A )

( B )

( B )

ME-00179

ME-00180

Unit: mm (in)

Bearing

Bearing size

(Thickness at cen-

ter)

Outer diameter of 

crank pin

Standard

1.492 — 1.501

(0.0587 — 0.0591) 

51.984 — 52.000

(2.0466 — 2.0472) 

0.03 

(0.0012)

undersize

1.510 — 1.513

(0.0594 — 0.0596) 

51.954 — 51.970

(2.0454 — 2.0461) 

0.05 

(0.0020)

undersize

1.520 — 1.523

(0.0598 — 0.0600) 

51.934 — 51.950

(2.0446 — 2.0453) 

0.25 

(0.0098)

undersize

1.620 — 1.623

(0.0638 — 0.0639) 

51.734 — 51.750

(2.0368 — 2.0374) 

ME-00181

ME-00174