BBM RB 4340 Forged Crank 4.375 Stroke

The EAGLE BBM RB 4340 Forged Crank with 4.375 Stroke is a premium crankshaft engineered for Mopar RB-series and 426 Hemi engine builds. This forged steel component delivers the internal balance and structural integrity required for high-performance applications, whether for street engines, racing platforms, or restoration projects demanding OEM-specification reliability. The 4.375-inch stroke geometry establishes the displacement and RPM characteristics fundamental to your engine's power delivery and torque profile.

Forged construction provides superior strength compared to cast alternatives, critical when managing higher cylinder pressures or extended duty cycles. The internal balance design eliminates the need for external balancing weights, simplifying installation and reducing rotating mass. The two-piece seal configuration ensures reliable oil containment at both ends of the crankshaft, preventing leakage during extended operation. The 8-bolt flange mounting interface maintains compatibility with Mopar RB-series block specifications, confirming drop-in fitment without modification to existing engine hardware.

This crankshaft is engineered for builders and restorers working with classic Mopar platforms where displacement and stroke geometry directly impact performance characteristics. Whether assembling a numbers-correct 426 Hemi replica, upgrading a street engine, or building a race-ready platform, the 4.375 stroke defines your displacement window and establishes baseline performance parameters. Proper installation requires attention to bearing clearances, bolt torque specifications, and balancing verification—standard practice for any quality machine shop or experienced engine builder.

At 75 pounds, the forged crank represents significant rotating mass that directly influences engine inertia, throttle response, and fuel consumption across the RPM range. Builders selecting this component should verify complete compatibility with their intended fuel system, ignition timing curve, and transmission pairing to optimize performance within their specific application parameters.