21-4N Single Intake Valve, 36mm +1mm Head

The GSC Power-Division 21-4N Single Intake Valve is engineered to be the best performing and longest-lasting valve available for the aftermarket. Utilizing advanced 3D design and simulation software, GSC has developed a stronger, higher-flowing valve head design that undergoes flow testing in specific applications to ensure it's the highest flowing on the market. Constructed from a modified 21-4N stainless steel material, this intake valve features a 36mm head with a +1mm size increase and a chrome polished finish. The design includes swirl-polished heads for improved airflow and a back-cut to reduce valve weight, allowing for higher RPM, increased boost pressure, and more aggressive cam profiles without needing higher valve spring seat pressures. The valve tips are hardened or feature a fused stelite wafer tip for extended life and reduced wear, and the keeper groove is adjusted to balance spring pressures, minimizing the need for shims and maximizing performance with GSC spring and retainer kits. These valves are compatible with OEM keepers/locks or GSC's upgraded versions. This single intake valve is specifically designed as a direct-fit replacement for Subaru BRZ (2013-2023) and Scion FR-S (2014-2016) models equipped with the FA20 engine.