BC0137 – Mitsubishi 4B11 Evo X Stroker Kit – 98mm Stroke/I-Beam Rods

Unlocking Maximum Displacement: The BC0137 4B11 Stroker Kit by Brian Crower

For the dedicated Mitsubishi Lancer Evolution X builder targeting the pinnacle of naturally aspirated torque or monumental forced induction potential, displacement is the ultimate foundation. The Brian Crower BC0137 Stroker Kit is a no-compromise engineering solution designed to transform the robust 4B11 engine into a displacement monster. This isn’t merely an assembly of parts; it’s a balanced, blueprint-level system centered around a massive 98mm stroke billet crankshaft, matched with premium 4340 Chromoly I-Beam connecting rods and forged pistons. Engineered for those who understand that cubic inches (or centimeters) are the first and most critical victory in the war for power, this kit provides the architectural shift necessary to dominate both street and strip, pushing the 4B11 platform far beyond its factory constraints.

Precision Engineering for Unyielding Performance

The core philosophy of the BC0137 kit is to increase displacement while simultaneously enhancing strength and rotational stability. The factory 4B11 crankshaft is a capable component, but it becomes the limiting factor for high-stroke applications and extreme cylinder pressures. Brian Crower addresses this by furnishing the kit with a 4340 Chromoly Steel Billet Crankshaft, featuring the critical 98mm stroke. Manufactured from a single billet, this crank offers superior grain structure and fatigue resistance compared to a cast or even a forged unit. Each unit is precision-machined, micro-polished, and shot-peened to achieve optimal surface finish and relieve stress points, resulting in a component that can withstand the tremendous inertial and torsional loads of a high-stroke, high-RPM setup.

Connecting this increased stroke to the piston are Brian Crower’s renowned 4340 Chromoly I-Beam Connecting Rods. The I-beam design is selected for its optimal balance of strength-to-weight ratio and rigidity under compression. Machined from premium 4340 Chromoly steel forgings, these rods undergo a heat-treating process to a tensile strength of 180,000 PSI, followed by shot peening and Magnaflux inspection to ensure zero flaws. The use of ARP 2000 cap screws (3/8″) as standard ensures the rod cap remains secured under even the most detonation-prone conditions, a common concern in high-boost stroker applications. The rods are balanced and weight-matched as a set, contributing to the engine’s overall smoothness and reducing harmonic vibrations.

To complete the rotating assembly, the kit includes custom forged aluminum pistons designed specifically for the increased stroke and rod combination. These pistons feature a robust dome design compatible with various combustion chamber configurations and are engineered with the appropriate valve reliefs for your selected camshaft profile. Manufactured from high-grade 2618 aluminum alloy, they prioritize ultimate strength and thermal stability over quiet operation, making them the unequivocal choice for high-performance and racing environments. Each piston is matched with a high-performance piston pin and SpiroLox pin retainers, completing a rotating assembly that is as durable as it is powerful.

Tangible Benefits of the 98mm Stroker Conversion

• Significant Displacement Increase: The 98mm stroke, combined with the appropriate cylinder bore, can increase total engine displacement to approximately 2.2L or more, providing a substantial boost in low-end torque and overall volumetric efficiency.
• Unmatched Rotating Assembly Strength: The billet crank and 4340 I-beam rod combination creates an immensely strong bottom end, capable of supporting well over 800+ horsepower with proper supporting mods, providing immense headroom for boost or nitrous.
• Improved Torque Curve: Increased displacement fundamentally improves an engine’s torque production, particularly in the low and mid-range RPM bands, resulting in faster spool for turbocharged applications and more responsive street performance.
• Engineered for High RPM: Despite the longer stroke, the balanced and lightweight design of the assembly allows it to safely sustain higher RPM limits than a stock assembly, ensuring power can be made across a wider band.
• Foundational for Maximum Power: This stroker kit establishes the strongest possible foundation for any subsequent performance upgrades, from aggressive camshafts to large-frame turbochargers, ensuring the bottom end will not be the point of failure.

Vehicle Fitment & Application Notes

The Brian Crower BC0137 Stroker Kit is engineered as a direct replacement rotating assembly for the Mitsubishi 4B11 engine platform. Primary fitment is for the 2008-2015 Mitsubishi Lancer Evolution X (CT9A). It is also compatible with other vehicles utilizing the 4B11 engine block, provided the engine builder accounts for external accessory and mounting differences. This is a serious competition-oriented component. Installation requires complete engine disassembly, professional machining of the engine block (including likely cylinder boring/honing to the piston size and possible block clearancing for the increased stroke), and assembly by a qualified machinist and engine builder. Proper bearing selection, clearancing, and final balancing of the entire rotating assembly (including the flywheel and damper) are absolutely mandatory for reliability.

Technical Specifications at a Glance

Selecting the BC0137 stroker kit is a commitment to building an absolute powerhouse. It represents a deep understanding of engine mechanics and a refusal to accept the factory limits of the 4B11 platform. For further technical reading on the principles of stroker engine design and its effects on engine dynamics, we recommend this insightful resource on engine theory and assembly practices from Engine Builder Magazine. When paired with expert machining, proper head work, and strategic airflow components, this Brian Crower kit lays the unshakable foundation for an Evo X engine that redefines expectations.