Description
The GSC Power-Division Billet S3 Camshaft Set is a top-tier valvetrain upgrade designed for extreme-performance Subaru EJ257 engines equipped with Dual AVCS. Manufactured by GSC Power-Division, the S3 camshafts are engineered specifically for high-boost, race-focused builds operating at very high horsepower levels and extended RPM ranges.
Precision-machined from billet steel, the S3 cam profile is the most aggressive in the lineup, designed for 750–1000+ WHP applications and a broad operating range of approximately 4500–9500 RPM. These camshafts prioritize maximum airflow and top-end power delivery, making them suitable for full race builds and heavily modified turbocharged setups.
To fully utilize the S3 camshafts, extensive engine modifications are required. A fully built bottom end is mandatory, with a sleeved or closed-deck block strongly recommended to handle the increased cylinder pressures associated with high boost and high RPM operation. In addition, fully built and ported cylinder heads are required, including necessary clearance work to accommodate the increased cam lift.
Upgraded valve springs are required to maintain proper valvetrain stability at high RPM. A standalone engine management system or advanced speed-density tuning setup is highly recommended to ensure proper idle quality, drivability, and safe engine operation.
Due to the aggressive lobe design, cylinder head casting clearance machining will be necessary during installation. Proper inspection and precision machining are essential to ensure correct fitment.
Proper break-in procedure using high-zinc oil is critical for camshaft longevity and correct surface bedding. Installation must be performed by an experienced engine builder familiar with high-performance Subaru platforms, and AVCS advance must be properly checked and calibrated during setup.
FITMENT
- 2008+ Subaru STI
- EJ257 engine with Dual AVCS
- Extreme high-horsepower built engines
- Suitable for 750–1000+ WHP race applications
KEY FEATURES
- Billet steel extreme-performance camshaft construction
- S3 race-spec aggressive cam profile
- Designed for 750–1000+ WHP builds
- Optimized for 4500–9500 RPM powerband
- Requires fully built bottom end (sleeved/closed deck recommended)
- Requires ported and modified cylinder heads
- High valve lift requires head clearance machining
- Valve spring upgrade required
- Standalone ECU or speed-density tuning highly recommended
- Maximum airflow and top-end power focus
- Designed for full race engine applications
INSTALL NOTES
- Verify camshaft orientation before installation (Long nose = Left side, Short nose = Right side)
- Head casting must be machined for clearance due to aggressive lobe design
- Proper break-in with high-zinc oil is required
- AVCS advance must be calibrated during installation
- Installation must be performed by an experienced engine builder only
