Michigan Motorsports LS1 & LT1 Harmonic Balancer Damper Bolt | OEM-Style Replacement for GM #12557840 | 4.8L–6.2L Wet Sump LS/LT Engines

Meet the Michigan Motorsports LS1 & LT1 Harmonic Balancer Crankshaft Damper Bolt — a high-strength, OEM-style replacement designed to secure your damper with confidence. This bolt is crafted to replace GM part number 12557840 and is compatible with GM wet sump engines ranging from 4.8L to 6.2L in LS and LT applications. Precision-machined for durability, it helps maintain crankshaft stability and minimizes vibration, whether you’re performing routine maintenance or building a high-performance engine.

Why choose this bolt? It combines robust materials with an exact fit to keep your damper properly aligned under load. The result is smoother operation, reduced rattles, and a solid foundation for your engine’s rotating assembly. Michigan Motorsports emphasizes reliability and fitment so you can proceed with confidence on both daily drivers and enthusiast builds.

Key benefits and fitment

• High-Strength Michigan Motorsports Quality — premium-grade materials built to handle torque and stress from daily driving to high-performance use.
• Direct GM Replacement — replaces GM part number 12557840 for an exact fit on LS1, LT1, and other compatible LS/LT wet sump applications.
• Wide GM Engine Compatibility — fits 4.8L, 5.3L, 5.7L, 6.0L, and 6.2L LS & LT engines (multiple variants including LS1, LS2, LS3, LT1, and more).
• Secure Damper Installation — maintains proper crankshaft alignment and minimizes vibration for smoother operation and longer engine life.
• Maintenance & Engine Builds — ideal for replacing worn factory bolts during rebuilds, upgrades, or harmonic balancer swaps.

Real-world use cases

From routine maintenance to performance-oriented builds, this bolt provides a dependable foundation for damper alignment. Enthusiasts who swap harmonic dampers or refresh a worn bolt during a rebuild will appreciate the exact GM-fitment and high-strength construction that supports consistent, quiet operation under load.

Installation notes

Because this part is an OEM-style replacement, it is designed to install with the same torque and clearance expectations as the original hardware. For best results, follow standard torque specs and ensure the damper is seated correctly before final tightening. This part is intended to help you achieve a reliable, long-lasting seal between the damper and crankshaft.