Subaru IMPREZA GD 2007 Series Manual page 2487

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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.
(A)
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 the piston.
NOTE:
• The top ring and second ring have the mark to
determine the direction to install on them. When in-
stalling them to piston, face this mark to the top
side.
• Oil ring consists of the upper rail, expander and
lower rail. When installing oil ring on piston, be
careful of the direction of each rail.
(A) Upper rail
(B) Expander
(C) Lower rail
Cylinder Block
2) Squarely place the piston ring and oil ring in cyl-
inder using the piston, and measure the piston ring
closed gap with a thickness gauge.
Piston ring
closed gap
ME-00175
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)
(B)
(C)
Ring groove
gap
(A)
(B)
(C)
ME-02472
ME(H4DOTC)-86
Unit: mm (in)
Standard
0.20 — 0.25
Top ring (0.0079 — 1.0 (0.039)
0.0098)
Second 0.37 — 0.52
1.0 (0.039)
ring (0.015 — 0.020)
0.20 — 0.50
Oil ring
(0.0079 — 1.5 (0.059)
rail
0.0197)
ME-00177
Unit: mm (in)
Standard
0.040 — 0.080
Top ring (0.0016 —
(0.0059)
0.0031)
0.030 — 0.070
Second
(0.0012 —
ring (0.0059)
0.0028)
ME-00178
Limit
Limit
0.15
0.15