Spec Clutch SF05A Billet Aluminum Flywheel SFI 1.1 Certified 157-Tooth 50oz External Balance

The Spec Clutch SF05A is a billet aluminum flywheel precision-engineered for high-performance street and racing applications. CNC-machined to an industry-leading .001-inch tolerance — ten times tighter than the industry standard of .010 — this flywheel delivers exceptional rotational balance, a perfectly flat clutch disc seating surface, and long-term drivetrain reliability.

Unlike generic lightweight flywheels, the SF05A is a tuned billet flywheel developed and weighted to optimize how the vehicle responds to changes in rotating mass in specific driving environments. The result is a flywheel that improves throttle response and helps maximize power delivery without sacrificing drivability.

Key Features:

• Aircraft-grade billet aluminum construction — significantly lighter than stock cast steel flywheels to reduce rotational mass and improve engine response
• CNC-machined to .001-inch tolerance — guarantees a flat, true seating surface for the clutch disc and eliminates dimensional runout
• SFI 1.1 certified — meets SFI safety standards for competition and performance use
• 157-tooth ring gear for proper starter engagement
• 50 oz. external balance — matches factory 302/5.0L external balance specification
• Replaceable steel friction plate — the rebuildable design uses a friction-enhancing steel insert specially formulated for optimum clutch bedding and clamping performance
• Diaphragm pressure plate compatible — designed for use with diaphragm-style clutch assemblies
• 11.0 lb. weight — lightweight aluminum construction reduces parasitic drivetrain loss
• 13.28-inch diameter

The flywheel plays a critical role in overall clutch system performance. It must provide a consistent friction surface for the clutch disc, manage inertia to optimize the power-to-acceleration ratio, and maintain true rotational balance at all RPM levels. The SF05A addresses all three requirements with precision manufacturing and application-specific engineering.

The aluminum flywheel body is rebuildable and features a replaceable steel friction plate — extending the service life of the flywheel and protecting your investment over time. This SF05A is engineered for 50 oz. externally balanced engines; for 28 oz. imbalance applications, see part number SF82A, and for neutral/internally balanced motors, see SF01A.