Subaru Legacy IV (2008 year). Manual - part 487

ME(H6DO)-74

Cylinder Block

MECHANICAL

4) How to measure the outer diameter of each pis-
ton:
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:

37.3 mm (1.4685 in)

Piston outer diameter:

Standard

A: 89.205 — 89.215 mm (3.5120 — 3.5124 in)
B: 89.195 — 89.205 mm (3.5116 — 3.5120 in)

0.25 mm (0.0098 in) oversize

89.445 — 89.465 mm (3.5215 — 3.5222 in)

0.50 mm (0.0197 in) oversize

89.695 — 89.715 mm (3.5313 — 3.5321 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)

6) Boring and honing:

(1) If the value of cylindrically, out-of-round-
ness, or cylinder-to-piston clearance measured
is out of standard or if there is any damage on
the cylinder wall, rebore it to use 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.

(2) If the cylinder inner diameter exceeds the
limit after boring and honing, replace the cylin-
der block.

Cylinder inner diameter boring limit (diameter):

To 89.715 mm (3.5321 in)

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.

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)

ME-00172

ME-00173

ME-00174

ME(H6DO)-75

Cylinder Block

MECHANICAL

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.

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 part of
the same size as piston.

NOTE:
• The top ring and second ring have the mark to
determine the direction to install on them. When in-
stalling the ring to piston, face this mark to the top
side.
• Oil ring consists of the upper rail, expander and
lower rail. When installing on the piston, be careful
of the direction of each rail.

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

3) Fit the piston ring straight into the piston ring
groove, then measure the clearance between pis-
ton ring and piston ring groove with a thickness
gauge.

NOTE:
Before measuring the clearance, clean the piston
ring groove and piston ring.

(A) Top ring

(B) Second ring

(a) Upper rail

(b) Expander

ME-00175

(A)

(a)

(c)

(b)

(A)

(B)

(C)

ME-00591

Standard

mm (in)

Piston ring gap

Top ring

0.20 — 0.35

(0.0079 — 0.0138)

Second ring

0.35 — 0.50

(0.0138 — 0.0197)

Oil ring

0.20 — 0.60

(0.0079 — 0.0236)

Standard

mm (in)

Clearance
between piston
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)

Clearance between oil ring and oil
ring groove

0.045 — 0.125

(0.0018 — 0.0049)

ME-00592

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ME(H6DO)-76

Cylinder Block

MECHANICAL

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 it has the
bend or twist.

3) Install the connecting rod fitted with bearing to
crankshaft and measure the thrust clearance. If the
thrust clearance exceeds the standard or uneven
wear is found, 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 each connecting
rod bearing using plastigauge. If any oil clearance
is not within the standard, replace the defective
bearing with a new part of standard size or under-
size as necessary. (See the table below.)

Connecting rod oil clearance:

Standard

0.016 — 0.043 mm (0.0006 — 0.0017 in)

6) Inspect the bushing at connecting rod small end,
and replace if worn or damaged.
7) Measure the piston pin clearance at connecting
rod small end. If the measured value is not within
the standard, replace it with a new part.

Clearance between piston pin and bushing:

Standard

0 — 0.022 mm (0 — 0.0009 in)

(A) Thickness gauge

(B) Connecting rod

( A )

( B )

ME-00179

ME-00180

Unit: mm (in)

Bearing

Bearing size

(Thickness at center)

Outer diameter of

crank pin

Standard

1.490 — 1.506

(0.0587 — 0.0593)

51.984 — 52.000

(2.0466 — 2.0472)

0.03

(0.0012)

undersize

1.509 — 1.513

(0.0594 — 0.0596)

51.954 — 51.970

(2.0454 — 2.0461)

0.05

(0.0020)

undersize

1.519 — 1.523

(0.0598 — 0.0600)

51.934 — 51.950

(2.0446 — 2.0453)

0.25

(0.0098)

undersize

1.619 — 1.623

(0.0637 — 0.0639)

51.734 — 51.750

(2.0368 — 2.0374)

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ME(H6DO)-77

Cylinder Block

MECHANICAL

8) The replacement procedure for the connecting
rod small end bushing is as follows.

(1) Remove the bushing from connecting rod
with ST and press.
(2) Press the bushing with ST after applying oil
on the periphery of bushing.

18350AA000

CONNECTING ROD
BUSHING REMOVER AND
INSTALLER

(3) Make two 3 mm (0.12 in) holes in the
pressed bushing by aligning with the pre-manu-
factured holes on the connecting rod, and ream
the inside of the bushing.
(4) After completion of reaming, clean the bush-
ing to remove chips.

6. CRANKSHAFT AND CRANKSHAFT
BEARING

1) Clean the crankshaft completely, and check it for
cracks using liquid penetrant tester. Replace if de-
fective.
2) Check the crankshaft for bend, and repair or re-
place if needed. Repair or replace if bended.

NOTE:
If a suitable V-block is not available, install #1 and
#5 crankshaft bearing on cylinder block, position
the crankshaft on these bearings, and then check
the crankshaft bend using a dial gauge.

3) Inspect the crank journal and crank pin for wear.
If they are not within the specification, replace the
bearing with a suitable (undersize) one, and re-
place or readjust crankshaft as necessary. When
grinding the crank journal or crank pin, finish them
to the specified dimensions according to the under-
size bearing to be used.

Crank pin and crank journal:

Out-of-roundness

0.005 mm (0.0002 in)

Cylindricality

0.006 mm (0.0002 in)

ME-00597

ME-00598

ME-00184

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