BC0624 – Subaru EJ257B (Dual AVCS – STi 08-up) Stage 3 Camshafts – Race Spec

For the builder who views the engine not as an assembly of parts, but as an air pump whose efficiency dictates power, the BC0624 Stage 3 Race Spec camshafts from Brian Crower represent the definitive recalibration of the Subaru EJ257B’s breathing architecture. Engineered explicitly for the Dual AVCS-equipped STi motors from 2008 and onward, this set transcends typical “bolt-on” cam upgrades. It is a core component in a system-wide strategy to unlock the true volumetric potential of the turbocharged boxer, moving the power band decisively into the high-RPM domain where race-winning horsepower is made. This isn’t merely an improvement; it’s a transformation of engine character, demanding supporting modifications and a precise tune to deliver earth-shattering results on dyno and track.

Engineering Philosophy: The Race Spec Profile

Brian Crower’s Race Spec nomenclature is a promise of extreme performance, and the BC0624 cams fulfill it through aggressive, asymmetrical lobe designs. Unlike street-oriented profiles that prioritize low-end manners, the Stage 3 grind implements a high-lift, long-duration strategy with a focus on area under the curve. The increased lift, typically in the range of 12.8mm, pushes the valve further into the combustion chamber, drastically enlarging the available port area for airflow at the most critical point in the cycle. Coupled with extended duration, this allows the cylinder to fill more completely at engine speeds where the inertial effects of the intake and exhaust tracts are working in the engine’s favor. The asymmetrical design—often featuring a more aggressive exhaust lobe—is calibrated to optimize scavenging in a turbocharged application, using exhaust pulse energy to not only evacuate spent gases more efficiently but also to draw in the fresh intake charge, effectively “supercharging” cylinder filling.

Dual AVCS Compatibility: Precision Timing Control

A critical differentiator for the EJ257B platform is its Dual Variable Valve Timing system, controlling both intake and exhaust camshaft phasing. The BC0624 camshafts are precision-machined to maintain full OEM AVCS functionality. This is non-negotiable. The cam gears interface perfectly with the factory phasers, and the cam profiles are designed with the expectation that the ECU will actively manage timing across the RPM range. This allows a competent tuner to use advanced strategies, such as retarding exhaust timing at low RPM for better torque and advancing it at high RPM for peak power, maximizing the benefit of the aggressive lobes. For in-depth technical analysis on AVCS tuning strategies, refer to this authoritative resource on optimizing Subaru’s Dual AVCS for power.

Performance Gains and Application Requirements

Expectations must be calibrated for a component of this caliber. The BC0624 cams are designed for engines where all other systems have been elevated to a matching level. On a fully built engine with supporting modifications—including a large-frame turbocharger (GTX3582R or larger), ported heads, high-flow fuel system, and a robust engine management tune—these cams can support power levels in excess of 600+ wheel horsepower. The power curve will characteristically shift upward, with significant gains manifesting from approximately 4,500 RPM to the 8,000+ RPM redline. Idle will be lumpy and aggressive, a hallmark of the significant overlap. This is not a component for a daily-driven car with a stock turbo; it is the final piece in a high-horsepower, competition-oriented powertrain.

• Extreme High-RPM Horsepower: Unlocks the final 15-20% of power potential in a built motor by maximizing volumetric efficiency at peak engine speeds.
• Superior Exhaust Scavenging: Asymmetrical profile reduces pumping losses and lowers exhaust gas temperatures (EGT), promoting detonation resistance.
• Maintained AVCS Functionality: Enables modern, precise tuning of the power band, allowing the tuner to tailor torque delivery.
• Engineered for Forced Induction: Lobe separation and overlap are optimized for turbocharged applications, balancing boost pressure and flow.
• Manufactured from Premium Materials: Made from high-grade alloy steel billet, heat-treated for exceptional wear resistance and longevity under extreme spring pressures.

Technical Specifications Table

Vehicle Fitment & Installation Notes

Primary Application: Subaru Impreza WRX STi (2008-2021) equipped with the EJ257B engine featuring Dual AVCS. This includes sedan and hatchback models. Critical Note: These cams are specifically for the later-model Dual AVCS engines. They are NOT compatible with single-AVCS (intake only) EJ257 engines found in 2004-2007 USDM STi models.

Installation is a major engine service requiring removal of the timing assembly, valve covers, and cam gears. It is imperative to use the correct assembly lube on the cam journals and lobes during installation. Valve lash must be checked and adjusted to Brian Crower’s specified clearance using bucket tappets, a process requiring precise measurement and potential shim selection. Failure to set correct lash will result in poor performance, valvetrain noise, and potential mechanical failure. Post-installation, a professional dyno tune is absolutely mandatory to calibrate fuel, ignition, and AVCS maps for the new cam profile. Engine break-in procedures per the cam manufacturer must be followed scrupulously.

System Synergy: The Built Engine Ecosystem

The BC0624 camshafts are the cerebral cortex of the high-performance EJ257B, but they require a capable body. To realize their potential, the entire valve train must be upgraded to handle the increased lift and ramp rates—think beehive or dual-spring setups with titanium retainers. The rotating assembly must be balanced and fortified. Most critically, the turbocharger and exhaust system must be of sufficient flow capacity; these cams will expose the bottleneck of a small turbine housing immediately. When integrated into a holistic performance build, the BC0624 Stage 3 Race Camshafts provide the authoritative, high-RPM breathing signature that separates championship-winning setups from the rest of the field.