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CP CPN-3327 ring pack provides exact fit for SC7021 pistons in Subaru WRX STI EJ257 engines. Built for 2004-2021 models this set ensures reliable compression sealing during extreme boost and high RPM. Perfect for engine rebuilds that demand consistent power delivery and durability.
Key Features
- Chrome Faced Top Ring: 1.2mm steel ring with chrome plating reduces friction and resists blow-by in turbo applications.
- Exact Piston Match: Sized for 99.75mm bore SC7021 pistons ensures zero gap issues and full face contact.
- Nitrided Second Ring: 1.5mm cast iron construction wears slowly maintains seal during high heat cycles.
- Flex-Vent Oil Ring: 2.8mm three-piece design controls oil effectively minimizes drag for freer revving.
- Pre-Honed Finish: Factory gaps set to Subaru specs 0.45-0.55mm top ring for quick break-in and long life.
- Forged from 2618 T6 aluminum with advanced coatings.
Fitment
| Fitment Basis | Universal by exact engine-component dimensions and interface |
|---|---|
| Required Verification | Bore diameter, ring thickness, groove configuration, material, coating, cylinder finish, and required end gap |
Specifications
| Manufacturer | CP Pistons |
|---|---|
| Manufacturer Part Number | CPN-3327 |
| Product Type | Piston Rings |
| Fitment Type | Universal by exact dimensions and interface |
What's Included
- One new CP Pistons piston ring set in the exact configuration and quantity identified by part number CPN-3327
- Pins, locks, rings, and installation components only when expressly listed for this exact part number
About CP Pistons
CP Pistons develops forged pistons, piston rings, wrist pins, and related engine components for performance applications. Correct selection and assembly depend on the exact engine, dimensions, cylinder head, connecting rod, intended use, machine work, clearances, and manufacturer part number.
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Browse the CP Pistons collection for related forged pistons, rings, pins, locks, and engine-building components.
Frequently Asked Questions
How do I select the correct CP piston ring set?
Match the exact bore diameter, ring diameters and thicknesses, groove configuration, material and coating, cylinder finish, intended use, and manufacturer part number.
Are piston rings ready to install without checking end gap?
Do not assume that. Measure every ring in its assigned cylinder and set end gap according to the current CP instructions for the bore, ring material, power level, fuel, boost, and intended use.
Which cylinder-wall finish should be used?
The required hone finish depends on the exact ring material and coating. Follow CP and ring-manufacturer specifications and have a qualified machine shop verify the finished bore.
Installation Instructions
Professional engine machining and assembly are required. Follow the current CP Pistons and engine-builder instructions for this exact part number. Measure every bore and component, verify all clearances and ring gaps, clean all parts and oil passages, use the specified lubricants and fastener procedures, confirm rotating-assembly and piston-to-valve clearance, and complete the required break-in and calibration.
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