GM LS Steel Harmonic Balancer SFI 25% U/D

The GM LS Steel Harmonic Balancer SFI 25% U/D from Power Bond Balancers is a precision-engineered crankshaft damper designed for high-performance LS-engine builds that demand race-grade reliability. This underdrive harmonic balancer reduces parasitic accessory load by 25 percent, freeing additional horsepower and torque for the wheels while minimizing heat generation in extreme engine conditions. Built for serious LS enthusiasts, bracket racers, and street performance applications, this balancer delivers the SFI 18.1 certification required by sanctioning bodies and high-power engine platforms.

Constructed from premium steel with a durable black paint finish, the balancer features internal balance design that integrates directly with LS-series crankshaft geometry without requiring external counterweights. The 6.220-inch outer diameter profile maintains stock-style compatibility while the SFI 25.1-rated construction meets modern racing safety standards for forced-induction and naturally aspirated LS engines. The underdrive configuration reduces belt speed to accessory drives (alternator, water pump, power steering), allowing each component to operate more efficiently while lowering parasitic drag and improving overall engine efficiency—a critical advantage during sustained high-RPM operation or heavy boost scenarios.

This harmonic balancer is ideal for LS-powered street rods, truck builds, and dedicated race engines where every horsepower matters and component longevity cannot be compromised. The internal-balance design ensures seamless fitment without modification to factory timing cover or accessory mounts, making installation straightforward on stock or custom LS blocks. Whether you're building a 5.3L truck engine, a 6.0L performance platform, or a 7.0L race mill, this SFI-certified underdrive balancer delivers measurable power gains while maintaining the structural integrity demanded by high-compression, boosted, or nitrous-fed applications.