CP Piston & Ring Set for Subaru EJ257 WRX STI- Bore (100.0mm)-Size (+0.5mm)- CR (9.0) - Set of 4

This is a set of four forged pistons and rings from CP Pistons, specifically made for the 2004-2012 Subaru Impreza with the EJ257 engine. These are a +0.5mm oversize set, meaning they are designed to be used when the engine cylinders have been bored out to 100.0mm. The compression ratio is set at 9.0:1, which is a common target for modified or performance-oriented builds where you might be using different camshafts or cylinder heads.

CP Pistons are well-known in the performance engine building world. They use strong, lightweight aluminum alloys for their forgings, which can handle the increased stress and heat that comes with a performance engine. The forging process itself creates a stronger grain structure than casting, making these pistons much more durable under demanding conditions. This set includes the pistons and the necessary rings, ready for installation by a professional engine builder. The 100.0mm bore size and +0.5mm oversize are critical details to ensure these fit correctly after your engine has been machined to match.

When rebuilding or modifying an EJ257 engine, choosing the right pistons is crucial for reliability and performance. This set from CP Pistons is a solid option for those looking to build a robust engine capable of handling more power. Remember that these pistons are not CARB approved and cannot be shipped to California. Always consult with your engine builder or refer to the manufacturer's installation instructions for precise fitting and assembly details.