BC8878 Brian Crower Polaris Adjustable Cam Gears – Intake & Exhaust Pair

For the dedicated Polaris RZR builder seeking to extract maximum efficiency and power from their engine, the Brian Crower BC8878 Adjustable Cam Gears represent a critical upgrade from the factory fixed-gear system. Engineered as a matched pair for both the intake and exhaust camshafts, these gears provide precise, degreeable control over cam timing, a fundamental parameter for optimizing volumetric efficiency across the entire RPM band. Whether you’re fine-tuning a heavily modified XPTurbo for desert dominance, seeking mid-range torque for technical trails on an XP1000, or optimizing a 570 for recreational use, these gears are the definitive tool for professional-level engine calibration. Manufactured from high-grade 6061-T6 billet aluminum and utilizing durable steel cam bolts and thrust plates, the BC8878 set translates theoretical tuning advantages into reliable, on-terrain performance gains.

The Engineering Imperative for Adjustable Cam Timing

Factory cam gears are pinned or keyed in a fixed position, locking cam timing to a single, compromise-oriented specification designed for broad emissions compliance, fuel economy, and longevity under warranty constraints. This one-size-fits-all approach severely limits the potential of aftermarket camshafts, ported heads, and forced induction systems. The Brian Crower BC8878 gears unlock this constraint. By allowing independent adjustment of the intake and exhaust camshafts in relation to the crankshaft, a tuner can advance or retard cam timing to tailor the engine’s personality. Advancing cam timing generally improves low-end and mid-range torque, while retarding timing can boost high-RPM horsepower. The ability to dial in overlap (the period where both intake and exhaust valves are open) is particularly crucial for turbocharged applications like the XPTurbo, where optimizing scavenging reduces exhaust backpressure and lowers intake charge temperatures.

Key Construction & Material Specifications

The integrity of an adjustable gear is non-negotiable; failure here is catastrophic. Brian Crower addresses this with a robust design. The gear body is CNC-machined from 6061-T6 billet aluminum, chosen for its excellent strength-to-weight ratio and machinability, ensuring perfect concentricity and tooth engagement. The adjustment mechanism employs three high-grade steel locking bolts that secure the inner hub to the outer gear ring via a precision-machined slotted pattern, preventing any movement under extreme harmonic vibration. Crucially, the kit includes a thrust plate system that replaces the stock wave washer, positively locating the camshaft and eliminating the potential for cam walk—a common concern in high-RPM Polaris ProStar engines. Every component is finished to aerospace tolerances, ensuring a perfect fit on OEM or aftermarket camshafts.

• Precision Engine Tuning: Enables fine-tuning of power delivery (torque vs. horsepower) for specific uses—dunes, rocks, trails, or competition.
• Unlocks Aftermarket Cam Potential: Mandatory for proper installation of aftermarket performance camshafts to achieve advertised power curves.
• Optimizes Forced Induction: Critical for tuning turbocharged (XPTurbo) applications to manage boost, spool time, and exhaust scavenging.
• Corrects Manufacturing Tolerances: Allows compensation for slight deviations in block, head, or timing chain dimensions for perfect timing.
• Enhanced Durability Package: Billet aluminum construction and steel thrust plate provide superior resistance to wear and cam walk compared to stock.

Installation Protocol & Tuning Methodology

Installation of the BC8878 gears requires mechanical competence and essential tools, including a degree wheel, dial indicator, magnetic base, and a quality torque wrench. The process begins with establishing true Top Dead Center (TDC) for cylinder #1. After removing the stock fixed gears, the Brian Crower units are installed with the timing marks aligned to the factory baseline position. The real work begins with degreeing the camshaft. Using the dial indicator to measure exact valve opening and closing events, the tuner compares these readings to the camshaft manufacturer’s spec card. Deviations are corrected by loosening the three locking bolts and rotating the inner hub relative to the outer gear—typically in 1-2 degree increments—before re-torquing to specification. This process is repeated for both intake and exhaust cams. For a deep dive into the science of cam timing, refer to this authoritative resource on camshaft degreeing basics from the experts at DSPORT Magazine.

Vehicle Fitment: Application-Specific Considerations

The BC8878 is engineered for the Polaris ProStar engine platform. Correct fitment is paramount for proper timing chain alignment and engine operation.

Technical Specifications: BC8878 Adjustable Cam Gears

In the realm of Polaris performance, the Brian Crower BC8878 Adjustable Cam Gears are not merely an accessory but an essential instrument for engine development. They provide the foundational control needed to harmonize intake, exhaust, and combustion events with your specific modifications and riding style. This is the definitive upgrade for the builder who understands that real power gains are found not just in bolt-on parts, but in the precise synchronization of all moving components.