Description
The GSC Power-Division Billet S1 Camshaft Set is a high-performance valvetrain upgrade designed for the 2008+ Subaru STI equipped with the EJ257B Dual AVCS engine. Manufactured by GSC Power-Division, these camshafts are engineered to improve airflow, throttle response, and top-end power for both street performance and moderate turbo upgrades.
Precision-machined from billet steel, the S1 camshafts are designed to deliver a strong balance of midrange torque and high-RPM power, making them suitable for stock-frame turbo setups as well as upgraded turbo systems targeting up to approximately 500 WHP (GT35R level builds). This makes them a versatile choice for performance-oriented street and track applications.
The cam profiles are optimized for Dual AVCS operation, allowing improved cam timing control and enhanced engine efficiency across the powerband. This results in better spool characteristics, improved volumetric efficiency, and increased overall engine responsiveness.
Upgraded valve springs are required for proper operation due to the increased lift and aggressive cam profile. Beehive valve springs are strongly recommended for improved valvetrain stability, though not strictly mandatory depending on build configuration.
Due to the larger lobe design, minor head casting clearance work may be required during installation. This should be carefully checked and adjusted as needed during assembly to ensure proper fitment and safe operation.
FITMENT
- 2008+ Subaru STI
- EJ257B engine with Dual AVCS
- Compatible with stock frame turbo setups
- Suitable for upgraded turbo systems up to ~500 WHP (GT35R class)
KEY FEATURES
- Billet steel high-performance camshaft construction
- S1 performance profile for balanced street/track use
- Optimized for Dual AVCS operation
- Improved airflow and high-RPM power gains
- Supports stock and moderate turbo upgrades
- Strong midrange torque and top-end performance
- Valve spring upgrade required
- Beehive springs recommended for best results
- May require minor head casting clearance during installation
- Engineered for EJ257B Subaru STI platforms
INSTALL NOTES
- Verify camshaft placement before installation (Long nose = Left side, Short nose = Right side)
- Check valve-to-head clearance during installation due to lobe size
- Professional installation strongly recommended
