0.50 Oversize Piston Ring Kit for Subaru Flat-Four ⚙️

Bring back strong compression and clean exhaust after a cylinder rebore (+0.50). This OEM-grade ring set is built for Subaru boxer engines, giving tight sealing, stable oil control, and long life under daily or spirited driving. Heat-treated steel rings with a moly-faced top ring reduce friction and wear, while the three-piece oil control ring keeps consumption low.

Why you need it 🔧

High mileage, scoring, or a hone/rebore demands new rings. Fresh rings restore cylinder pressure, cut blow-by, and stop blue smoke. Perfect for engine rebuilds where reliability and efficiency matter.

How it works 🛠️

Three rings per piston: the top ring seals combustion, the second scrapes and supports sealing, and the oil ring (with expander) meters oil on the wall. Correct tension and face design lock compression in, keep oil out of the chambers, and stabilize heat transfer.

If worn or broken 🚫

Expect hard starts, power loss, high fuel use, blue smoke, plug fouling, and rising crankcase pressure. Prolonged driving risks scored bores and catalytic converter damage.

Tech notes ✅

Hone to proper finish, clean bores, check end gaps, and stagger ring openings. Lubricate on install; verify piston-to-wall clearance for 0.50 oversize.

Compatibility

• Legacy
• Impreza
• Forester
• Exiga