Engines and Components› Pistons and Piston Rings

CP Pistons

CP Piston & Ring Set for Subaru EJ257 WRX STi - Bore (100mm) - Size (0.5mm) - CR (8.2)

$885.15

SKU: C00A SC7421-4

In Stock
In Stock
Ships by Jun 11
Free Shipping
Non-Returnable Item
INSTALL DIFFICULTY
DIY PRO SHOP

Advanced — 4+ hours

Description

The CP Piston Set is designed for high-horsepower and high-boost Subaru EJ25 Turbo models. These forged pistons have an 8.2:1 compression ratio and a 100mm bore, with deep valve relief for high lift camshafts and +1mm valve sizes. They feature a custom skirt cam and barrel design, accumulator grooves, and high-strength aluminum forgings. The set includes high-performance rings and wrist pins (with double pin oilers, force-fed oil ring), are fully CNC machined and balanced to +/- 1 gram, and include pin fitting.

Fitment

Fitment Guaranteed

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on fit.

Log your build in the MOTORMIA app and we’ll guarantee this part fits your exact setup — or your money back, return shipping covered.

Available on iOS & Android

Specifications

BrandCP Pistons
Part NumberC00A SC7421-4

Videos

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I Rebuilt My Subaru STI EJ257 Engine from Scratch!
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Subaru EJ25 Engine Build Tutorial - Step by Step Guide
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Buy with Confidence

Built for enthusiasts. Every order is backed by our 30 day return window on eligible items. Unused and uninstalled products may be returned with approved RMA and no restocking fees when received in new condition. Orders placed through the MOTORMIA app with a complete build qualify for our Fitment Guarantee — free return shipping if the part doesn’t fit your exact setup. The guarantee covers fit only; installation must follow manufacturer instructions, and we recommend a qualified shop for parts marked Difficulty 4–5.

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