CP Pistons SC7422-4 Forged Piston & Ring Set for 2004-21 Subaru EJ257 +0.25mm

Vehicle Fitment

• 2004-2021 Subaru WRX STI EJ257 2.5L Turbo
• 2006-2014 Subaru WRX EJ257 2.5L Turbo*
• 2009-2013 Subaru Forester XT EJ257 2.5L Turbo*

Features

• High-strength forged 2618 aluminum pistons
• Designed for +0.25mm oversize bore (99.75mm)
• Deep valve reliefs for high-lift cams and oversize valves
• Fully CNC machined and balanced to ±1 g
• Accumulator grooves to promote ring seal and reduced blow-by
• Double pin oilers for improved lubrication at wrist pins
• Lightweight design for quicker engine response
• Includes piston rings and wrist pins

Specifications

• Part Number: SC7422-4
• Bore Size: 99.75 mm (+0.25mm oversize)
• Compression Ratio: ~8.2:1
• Stroke: 79 mm
• Rod Length: 130.5 mm
• Pin Diameter: 23 mm
• Ring Pack: 1.2 mm/1.2 mm/2.0 mm
• Piston Weight: ~399 g

Included Components

• 4x Forged pistons (99.75 mm +0.25mm)
• 4x Piston ring sets
• 4x Wrist pins

Product Description

The **CP Pistons SC7422-4 forged piston and ring set** is engineered for high-performance Subaru EJ257 turbocharged engines found in WRX STI and compatible EJ257 WRX/Forester XT applications. This set features premium 2618 aluminum forgings that are CNC machined and balanced to tight tolerances, making them suitable for high-boost builds, seasoned rebuilds, and engines that demand durability under elevated combustion pressures. The +0.25 mm oversize bore size (99.75 mm) expands upon the stock dimensions for restored performance after block machining or to support aggressive tuning goals.

Each piston incorporates performance-oriented features such as deep valve reliefs for high-lift camshaft compatibility, accumulator grooves for improved ring sealing, and double pin oilers for enhanced lubrication around the wrist pins. Complete with high-quality piston rings and wrist pins, the SC7422-4 set offers a comprehensive upgrade option for Subaru enthusiasts and engine builders looking to solidify engine reliability and broaden power potential in turbocharged EJ257 platforms.