Ferrea Valve Spring Kit for Subaru WRX STI Endurance Dual Spring

Ferrea Valve Spring Kit for Subaru WRX STI — Endurance Dual Spring Upgrade your Subaru WRX STI with the Ferrea Endurance Dual Spring Kit — engineered for high-performance engines, aggressive cam profiles, and track focused reliability. Designed specifically for Subaru EJ-series cylinder heads, this kit delivers consistent valve control under extreme RPM and load. Key Features Dual-spring design: Inner and outer springs for superior damping and reduced resonant harmonics. High spring rates: Prevents valve float at elevated RPM and supports aggressive cam timing. Durable materials: Heat-treated alloy steel for long life and fatigue resistance. Precision wound: Consistent seat and open pressures for predictable valve actuation. Direct fit: Made to fit Subaru WRX STI EJ engines with OE-compatible dimensions and retainers. Benefits Expect improved throttle response, safer high-RPM operation, and reduced risk of valve train failure during endurance or competitive use. Ferrea's quality control ensures repeatable performance for street, track, or race applications. Application & Compatibility Fits: Subaru WRX STI (EJ-series engines) Ideal for: High-lift cams, turbocharged builds, and endurance racing Install with confidence: Pair with Ferrea retainers, locks, and valve train components for a complete built package. Choose Ferrea for proven performance and durability.