Subaru Legacy (2005 year). Manual — part 285

ME(H4DOTC)-83

MECHANICAL

Cylinder Block

2. CYLINDER AND PISTON

1) The cylinder bore size is stamped on the cylinder
block’s front upper surface.

NOTE:
• Measurement should be performed at a temper-
ature of 20

°C (68°F).

• Standard sized pistons are classified into two
grades, “A” and “B”. These grades should be used
as guide lines in selecting a standard piston.

Standard diameter:

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

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.

(A) Main journal size mark

(B) Cylinder block (RH)

− (LH) combination mark

(C) #1 cylinder bore size mark

(D) #2 cylinder bore size mark

(E) #3 cylinder bore size mark

(F) #4 cylinder bore size mark

ME-00170

#5

#4

#3

#2

#1

(A)

(B)

(F)

(D)

A

B

A

B

5

4

5

4

(C)

(E)

(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(H4DOTC)-84

MECHANICAL

Cylinder Block

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:

40.0 mm (1.57 in)

Piston outer diameter:

Standard

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

0.25 mm (0.0098 in) oversize

92.245 — 92.265 mm (3.6317 — 3.6325 in)

0.50 mm (0.0197 in) oversize

92.495 — 92.515 mm (3.6415 — 3.6423 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)

6) Boring and honing:

(1) If the value of taper, out-of-roundness, or
cylinder-to-piston clearance measured exceeds
the 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, 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
92.515 mm (3.6423 in) after boring and honing,
replace the cylinder block.

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 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)-83, 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.

Standard clearance between hole in piston and
piston pin:

Standard

0.004 — 0.008 mm (0.0002 — 0.0003 in)

ME-00172

H

ME-00173

ME-00174

ME(H4DOTC)-85

MECHANICAL

Cylinder Block

4) Check the snap ring installation groove on the
piston for burr (A). 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 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 those marks upward.
• Oil ring consists of the upper rail, expander
and lower rail. When installing on piston, be
careful of each rail’s direction.

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

NOTE:
The difference between the outer and inner circle
side of top ring must be less than 0.05 mm (0.0020
in).

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

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

(A) Upper rail

(B) Expander

(C) Lower rail

ME-00175

(A)

ME-02480

(A)

(B)

(C)

(A)

(B)

(C)

Standard

mm (in)

Piston
ring gap

Top ring

Outer circle side: 0.20 — 0.25

(0.0079 — 0.0098)

Inner circle side: 0.20 — 0.30

(0.0079 — 0.012)

Second
ring

0.40 — 0.50

(0.016 — 0.020)

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(H4DOTC)-86

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 or offset
wear occurs, 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

0.026 — 0.052 mm (0.0010 — 0.0020 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 center)

Outer diameter of

crank pin

Standard

1.486 — 1.498

(0.0585 — 0.0590)

51.984 — 52.000

(2.0466 — 2.0472)

0.03

(0.0012)

undersize

1.504 — 1.512

(0.0592 — 0.0595)

51.954 — 51.970

(2.0454 — 2.0461)

0.05

(0.0020)

undersize

1.514 — 1.522

(0.0596 — 0.0599)

51.934 — 51.950

(2.0447 — 2.0453)

0.25

(0.0098)

undersize

1.614 — 1.622

(0.0635 — 0.0639)

51.734 — 51.750

(2.0368 — 2.0374)

ME-00181

ME-00174