BC0116 – Mitsubishi 4G64 Block/4G63 Head Stroker Kit – 102mm Stroke w/ ProH2K Rods

Forging the ultimate displacement foundation for the legendary 4G6x platform, the Brian Crower BC0116 Stroker Kit is not merely an upgrade—it is a complete re-engineering of your engine’s rotating assembly. Designed explicitly for the 4G64 (2.4L) block and 4G63 (2.0L) cylinder head combination, this kit systematically addresses the inherent limitations of factory components to unlock a new stratum of torque, horsepower, and reliability. By utilizing a massive 102mm stroke 4340 billet crankshaft paired with custom 6.141″ Pro Series H-Beam connecting rods and forged pistons, this package transforms your engine into a 2.5-liter torque monster, engineered for dominance in forced induction applications. Every component is precision-manufactured to Brian Crower’s exacting race standards, ensuring a perfect, balanced assembly that is ready for four-digit horsepower levels.

The Architecture of Displacement: 4G64 Block & 4G63 Head Synergy

The 4G63 cylinder head is revered for its robust casting, optimal port geometry, and legendary aftermarket support. The 4G64 block provides a taller deck height, offering the necessary cylinder bore and physical space for a significantly longer stroke. The BC0116 kit is the definitive bridge between these two iconic platforms. It capitalizes on the 4G64’s structural advantage to accept the 102mm stroke crankshaft, while the custom piston design corrects for the deck height difference and optimizes compression height and ring placement for use with the 4G63 head. This is not a parts-bin hybrid; it is a cohesive engineered system designed to function as a single, high-performance unit. The result is a substantial displacement increase from 2.4L to approximately 2.5L (exact displacement varies with final bore size), providing a profound increase in low-end and mid-range torque—the critical area where turbocharged engines often seek more leverage.

Core Component Analysis: The 4340 Billet Crankshaft

The heart of the BC0116 kit is the custom-manufactured 4340 chromoly billet steel crankshaft. The 102mm stroke represents a significant increase over the stock 4G64’s 100mm stroke, directly responsible for the displacement gain. Choosing a billet crankshaft over a forged or cast unit is a non-negotiable decision for serious performance.

• Material Superiority: Machined from a single, vacuum-degassed block of 4340 chromoly steel, the billet process allows for grain flow that follows the final contour of the part, creating exceptional strength and fatigue resistance at the critical journal fillets.
• Precision & Balance: Each crank is CNC-machined to exacting tolerances, featuring micro-polished journals for reduced friction and optimal oil film retention. It is internally balanced for the specific piston and rod combination in the kit, minimizing harmonic vibrations that can destroy main and rod bearings at high RPM.
• Enhanced Oiling: The crankshaft is cross-drilled and chamfered to ensure consistent, high-volume oil flow to the rod bearings under extreme load, a crucial feature for sustained high-RPM or high-boost operation.

Rotating Assembly: ProH2K Connecting Rods & Forged Pistons

To harness the power of the 102mm stroke, the connecting rods and pistons must be equally over-engineered. This kit includes Brian Crower’s Pro Series H2K rods and 2618 alloy forged pistons as a matched set.

ProH2K Connecting Rods (6.141″ Center-to-Center): This specific length is calculated to maintain a proper rod ratio with the 102mm stroke, optimizing piston motion and reducing side loading on the cylinder walls. Manufactured from 4340 chromoly steel, they feature a true H-beam design for ultimate strength in both tension and compression. The rods utilize ARP 2000 cap screws as standard, providing immense clamping force to keep the rod cap securely located under brutal combustion pressures.

Custom Forged Pistons: The pistons are the critical interface, and these are not off-the-shelf units. They are custom-designed with a compression height that positions the pin correctly for the 6.141″ rod and 102mm stroke within the 4G64 block. Manufactured from 2618 aluminum alloy, they prioritize ultimate strength and durability for high-horsepower, high-boost applications over tight cold-start clearance. They include fully floating wrist pins with spiral locks and feature a valve relief profile compatible with most aftermarket 4G63 camshafts. Ring land thickness is increased, and the piston is designed for a standard 1.5mm, 1.5mm, 3.0mm ring package.

Performance Benefits & Application Rationale

• Substantial Torque Multiplication: The increased displacement and stroke directly translate to greater cylinder filling and a longer lever arm, producing significantly more torque, especially in the low and mid-range RPM band. This makes the engine more responsive and reduces turbo lag.
• Foundation for Extreme Power: With a billet crank, Pro Series rods, and forged pistons, this rotating assembly is rated for horsepower levels exceeding 1500 HP, making it future-proof for virtually any power goal.
• Optimized Rod/Stroke Ratio: The carefully selected 6.141″ rod length helps maintain mechanical efficiency and reduces piston skirt friction and wear compared to a less-ideal ratio.
• Systematic Compatibility: Eliminates the guesswork and component mismatch common in DIY stroker builds. Every part is designed to work in unison, ensuring correct piston-to-valve, piston-to-deck, and ring placement geometry.
• Enhanced Durability: The superior materials and manufacturing processes of all components provide a massive safety margin over OEM and many forged offerings, crucial for high-stress drag, time-attack, or rally applications.

Vehicle Fitment & Critical Installation Notes

Primary Application: This BC0116 kit is engineered specifically for building a stroker engine using a Mitsubishi 4G64 (2.4L) engine block (typically from a 1994-1998 Mitsubishi Galant, Eclipse Spyder, or similar) combined with a Mitsubishi 4G63 (DOHC) cylinder head (from a 1G/2G DSM or Evo I-IX). The final assembly will require the use of the 4G63 timing components, front case, oil pump, and head.

Essential Considerations:

• Block Preparation: The 4G64 block must be bored and honed to the target final diameter (e.g., 87mm, 87.5mm) with torque plates to ensure perfect cylinder geometry. Block decking is highly recommended to achieve precise deck height and quench.
• Cylinder Head: Must be a 4G63 DOHC head. The 4G64 SOHC head is not compatible. Valvetrain and camshaft selection must account for the increased piston displacement and potential valve clearance.
• Balancing is Mandatory: While the kit components are balanced individually, a professional rotating assembly balance is absolutely required before final assembly. This includes balancing the crankshaft, rods, pistons, pins, rings, and bearings as a unit.
• Clearance Checking: Even with matched components, a thorough mock-up assembly to check piston-to-valve, piston-to-deck, and rod-to-block/cylinder wall clearance is non-negotiable for a reliable build.

For a deeper technical dive into the platform’s potential, refer to this authoritative engineering analysis on building a high-performance 4G63/4G64 hybrid engine.

Technical Specifications Table