{"product_id":"cp-piston-ring-set-for-subaru-ej257-wrx-sti-bore-99-5mm-size-standard-cr-8-2","title":"CP Piston \u0026 Ring Set for Subaru EJ257 WRX STi - Bore (99.5mm) - Size (Standard) - CR (8.2)","description":"\u003cp\u003e\u003cstrong\u003eSKU:\u003c\/strong\u003e \u003cspan itemprop=\"sku\"\u003eSC7420-4\u003c\/span\u003e\u003c\/p\u003e\n\n\u003ch4\u003e\u003cstrong\u003eCP Piston \u0026amp;amp. Ring Set for 2004-2021 Subaru Impreza WRX STI EJ257 - Bore 99.5mm Standard - CR 8.2\u003c\/strong\u003e\u003c\/h4\u003e\n\u003cp\u003eThis CP piston and ring set SC7420-4 delivers forged reliability for Subaru EJ257 turbo engines in 2004-2021 Impreza WRX STI models. The 99.5mm standard bore and 8.2:1 compression ratio handle aggressive boost levels up to 40+ psi while ensuring durability in high-performance builds. Engine builders rely on this set for precise tolerances, weight matching, and consistent power in rally and drag applications.\u003c\/p\u003e\n\n\u003ch4\u003eKey Features\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eForged 2618-T6 Aluminum:\u003c\/strong\u003e Delivers high strength-to-weight ratio to handle extreme cylinder pressures in turbocharged EJ257 engines\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e8.2:1 Compression Ratio:\u003c\/strong\u003e Supports safe high-boost operation up to 40+ psi with lower detonation risk for reliable track performance\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAccumulator Grooves:\u003c\/strong\u003e Trap combustion residue to prevent ring flutter and maintain tight seal under high boost conditions\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLow-Friction Skirt Coating:\u003c\/strong\u003e Cuts drag, reduces operating temperatures, and prolongs piston life during aggressive shifts and launches\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePremium Rings and Pins Included:\u003c\/strong\u003e Pre-gapped rings with tool steel pins and clips for drop-in assembly and immediate competition use\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch4\u003eProduct Notes\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003eSet includes 4 pistons, rings, wrist pins, and clips balanced to OEM specifications\u003c\/li\u003e\n\u003cli\u003eDesigned for stock 79mm stroke rods and crankshaft in EJ257 engines\u003c\/li\u003e\n\u003cli\u003eShips ready for professional engine assembly with CNC-machined precision\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch4\u003eInstallation Notes\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003eProfessional installation recommended.\u003c\/li\u003e\n\u003cli\u003eHone cylinders to 99.5mm with CP-specific ra finish for optimal ring seating\u003c\/li\u003e\n\u003cli\u003eCompatible with OEM connecting rods and bearings\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch4\u003eThis Part Fits\u003c\/h4\u003e\n\u003ctable border=\"1\"\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eYear\u003c\/th\u003e\n\u003cth\u003eMake\u003c\/th\u003e\n\u003cth\u003eModel\u003c\/th\u003e\n\u003cth\u003eSubmodel\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e2004-2021\u003c\/td\u003e\n\u003ctd\u003eSubaru\u003c\/td\u003e\n\u003ctd\u003eImpreza\u003c\/td\u003e\n\u003ctd\u003eWRX STI\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e2007\u003c\/td\u003e\n\u003ctd\u003eSubaru\u003c\/td\u003e\n\u003ctd\u003eImpreza\u003c\/td\u003e\n\u003ctd\u003eWRX STI Limited\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e2011-2012\u003c\/td\u003e\n\u003ctd\u003eSubaru\u003c\/td\u003e\n\u003ctd\u003eImpreza\u003c\/td\u003e\n\u003ctd\u003eWRX STI Limited\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e2010\u003c\/td\u003e\n\u003ctd\u003eSubaru\u003c\/td\u003e\n\u003ctd\u003eImpreza\u003c\/td\u003e\n\u003ctd\u003eWRX STI Special Edition\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e2006-2009\u003c\/td\u003e\n\u003ctd\u003eSubaru\u003c\/td\u003e\n\u003ctd\u003eLegacy\u003c\/td\u003e\n\u003ctd\u003eGT 2.5XT\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e2008-2014\u003c\/td\u003e\n\u003ctd\u003eSubaru\u003c\/td\u003e\n\u003ctd\u003eForester\u003c\/td\u003e\n\u003ctd\u003eXT\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003ch4\u003eWhy Choose CP Pistons?\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003eBuilt in USA with motorsports heritage in rally and drag racing\u003c\/li\u003e\n\u003cli\u003eCNC-machined for exact bore fit and weight matching to OEM standards\u003c\/li\u003e\n\u003cli\u003eEngineered for Subaru EJ257 turbo platforms with proven high-boost handling\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch4\u003e\u003cstrong\u003eFrequently Asked Questions\u003c\/strong\u003e\u003c\/h4\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eQ:\u003c\/strong\u003e Will SC7420-4 fit all EJ257 engines in 2004-2021 STI?\u003cbr\u003e\n      \u003cstrong\u003eA:\u003c\/strong\u003e Yes, direct fit for standard 99.5mm bore EJ257 in Impreza WRX STI models including Limited and Special Edition plus Legacy GT and Forester XT\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eQ:\u003c\/strong\u003e What material are these pistons made from?\u003cbr\u003e\n      \u003cstrong\u003eA:\u003c\/strong\u003e Forged 2618-T6 aircraft-grade aluminum with phosphate coating and moly skirt finish for heat resistance and low friction\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eQ:\u003c\/strong\u003e What warranty covers this piston set?\u003cbr\u003e\n      \u003cstrong\u003eA:\u003c\/strong\u003e Backed by CP Pistons limited warranty against manufacturing defects when installed by certified builders\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch4\u003eShipping \u0026amp; Handling\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eMethod:\u003c\/strong\u003e UPS Ground\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAvailability:\u003c\/strong\u003e In stock - ships same or next business day\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePackaging:\u003c\/strong\u003e Foam-inserted box measuring 12 x 10 x 4 inches\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWeight:\u003c\/strong\u003e 5.8 lbs\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"CP Pistons","offers":[{"title":"Default Title","offer_id":43720402763855,"sku":"CPPSC7420-4","price":885.15,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1062\/7920\/files\/cp-piston-ring-set-for-subaru-ej257-wrx-sti-bore-99_5mm-size-standard-cr-8_2-cp-pistons.jpg?v=1769636000","url":"https:\/\/www.blackopsautoworks.com\/products\/cp-piston-ring-set-for-subaru-ej257-wrx-sti-bore-99-5mm-size-standard-cr-8-2","provider":"Black Ops Auto Works","version":"1.0","type":"link"}