Manley 612000C-4 Platinum Pistons Subaru EJ257 2.5L 99.5mm STD 8.5:1 Dish Set/4

Vehicle Fitment

• 2006-2014 Subaru Impreza WRX (EJ257, 2.5L DOHC Turbo)
• 2004-2021 Subaru WRX STI (EJ257, 2.5L DOHC Turbo)
• 2004-2013 Subaru Forester XT (EJ257 / EJ255, 2.5L DOHC Turbo)
• 2005-2009 Subaru Outback XT (EJ255, 2.5L DOHC Turbo)
• 2005-2009 Subaru Legacy GT (EJ255, 2.5L DOHC Turbo)

Fitment Notes

• Fits the Subaru EJ257 2.5L engine at standard bore (99.50 mm) - verify bore size with a machine shop before ordering; cylinders must be honed to proper clearance even at standard bore
• Does NOT fit the 2002-2005 Subaru WRX - those models use the EJ205 2.0L engine with a different bore size; see the Manley 615000C-4 or similar for EJ205 applications
• Designed for standard 79mm stroke EJ257 applications - not compatible with stroker kits using a different crank throw
• Wrist pin diameter: 22mm (0.866 in.) - compatible with Manley 14024-4 and 15024-4 H-Beam / H-Tuff rods and other EJ257-spec aftermarket rods using a 22mm pin bore
• Will accommodate +1mm valve sizes without piston-to-valve interference
• Compression ratio of 8.5:1 is slightly higher than OEM EJ257 (8.2:1) - a thicker head gasket can be used to reduce compression ratio if needed; verify with your tuner
• Recommended piston clearance: 0.003 in. for mildly boosted builds / 0.0035 in. for highly boosted builds - measured 1.100 in. from the bottom of the oil ring
• Oversize bore options available separately (99.55mm, 99.75mm, 100.00mm) - order the 612000C-4 only for standard 99.50mm bore
• Professional engine builder installation required
• No manufacturer warranty - Manley Performance does not offer a warranty on pistons due to the performance-oriented nature of the product

Features

• Platinum Series forged 2618 aluminum alloy construction - 2618 alloy delivers maximum high-temperature strength, fatigue resistance, and durability under sustained high-boost, high-RPM conditions that would fracture OEM cast ring lands
• Dished top design (-22 cc dome volume) lowers compression ratio relative to a flat-top piston, enabling aggressive boost targets with pump or E85 fuel
• Offset wrist pin design reduces piston-to-cylinder wall impact at TDC for quieter cold starts and reduced slap during warm-up
• Moly-coated (anti-friction) skirts reduce friction against cylinder walls for improved break-in, reduced wear, and improved thermal management
• Pressure balance groove equalizes pressure across the top ring land for more consistent ring seal and improved combustion efficiency
• Proprietary multi-step top ring groove machining process ensures precise groove geometry, flatness, and finish for optimal ring sealing and maximum power
• Precise pinhole machining delivers exact compression distance and precise lock ring groove concentricity across all four pistons
• Lightweight design (~395 grams) reduces rotating assembly mass for improved throttle response and reduced reciprocating load on rod bearings
• Made in the USA to Manley's exacting standards used in professional motorsport and OEM supply applications

Specifications

• Series: Platinum Series
• Material: Forged 2618 Aluminum Alloy
• Piston Type: Dish (Dished Top)
• Bore Size: 99.50 mm (Standard Bore)
• Over Size: STD
• Stroke: 79 mm (Standard)
• Rod Length: 5.137 in.
• Compression Distance: 1.209 in.
• Dome Volume: -22 cc (Dish)
• Cylinder Head Volume: 51 cc
• Compression Ratio: 8.5:1
• Piston Weight: ~395 grams each
• Wrist Pin Diameter: 0.866 in. / 22mm
• Wrist Pin Wall: 0.150 in.
• Wrist Pin Length: 2.250 in.
• Wrist Pin Material: Premium Chrome Moly (Tool Steel)
• Skirt Coating: Moly (Anti-Friction)
• Piston Clearance (Mild Boost): 0.003 in. measured 1.100 in. from bottom of oil ring
• Piston Clearance (High Boost): 0.0035 in. measured 1.100 in. from bottom of oil ring
• Included Ring Set: Part #46995-4
• Quantity: Set of 4
• Country of Origin: USA

Included Components

• 4x Manley Platinum Series forged 2618 dished pistons (99.50mm, moly-coated skirts)
• 4x Premium Chrome Moly wrist pins (22mm / 0.866 in.)
• 4x Complete piston ring sets (Part #46995-4 - Premium Steel top ring, Napier-style second ring, higher-tension oil rings)
• 4x Round wire wrist pin locks

Product Description

The Manley 612000C-4 Platinum Series piston set is a complete forged piston solution for Subaru EJ257 2.5L engine rebuilds at standard bore (99.50mm). Machined from domestic 2618 aluminum alloy forgings, these pistons are engineered to withstand the ring land fractures, piston failures, and material fatigue that afflict OEM EJ257 cast pistons under elevated boost and power levels. The dished top design produces a 8.5:1 compression ratio - slightly higher than the OEM EJ257's 8.2:1, which is well within tune-able range for most builds and actually beneficial for maximizing power on pump gas or E85. The -22cc dish volume provides ample flexibility for pairing with various head gasket thicknesses to dial in the precise compression ratio required for your fuel and boost strategy.

Each piston features Manley's offset wrist pin design for reduced cold-start piston slap, a pressure balance groove for consistent ring seal, and moly-coated skirts for reduced friction and optimized break-in. The multi-step ring groove machining process ensures precise geometry across all four ring lands, while the "one fixturing" manufacturing method maintains perfect ring groove-to-skirt squareness for maximum power output and sealing integrity. At approximately 395 grams each, these pistons are lighter than many competing forged units, reducing rotating assembly mass and reciprocating loads on the rod bearings and crankshaft. The 22mm (0.866 in.) wrist pin diameter is fully compatible with Manley's 14024-4 H-Beam and 15024-4 H-Tuff connecting rods, as well as other EJ257-spec aftermarket rods using a standard straight 22mm pin bore.

The complete kit includes four pistons, four chrome moly wrist pins, four ring sets (Manley #46995-4 - Premium Steel top ring, Napier-style second ring, higher-tension oil rings), and four round wire wrist pin locks. Recommended piston-to-wall clearance is 0.003 in. for mildly boosted builds or 0.0035 in. for high-boost applications, measured 1.100 in. from the bottom of the oil ring. Cylinders must be honed to the correct clearance by a qualified machine shop, even on a standard-bore rebuild. Manley does not offer a warranty on performance pistons. Made in the USA and sold as a complete set of 4.