Spec Clutch SM664 Stage 4 Performance Clutch Kit - Carbon Semi-Metallic

The SPEC SM664 Stage 4 Clutch Kit is a race-grade performance clutch designed for heavily modified engines demanding maximum torque capacity and instantaneous engagement. Built around a solid 8-rivet hub that is heat-treated for exceptional strength and durability, this kit steps up from the Stage 3 by replacing the sprung hub with a rigid hub assembly for more direct, uncompromising power transfer.

The carbon semi-metallic friction disc is available in 3, 4, or 6-puck configurations to match your specific racing discipline. The 3-puck disc delivers the lightest rotating mass, the 6-puck provides the smoothest engagement of the puck options, and the 4-puck strikes a balance between the two. Note: due to the rigid hub design, this kit is not recommended for street use — it is engineered exclusively for competition applications.

Kit Contents:

• High-clamp performance pressure plate
• Carbon semi-metallic multi-puck friction disc (3, 4, or 6-puck)
• High-torque solid 8-rivet rigid hub and carrier assembly
• Release bearing
• Installation tool kit

Ideal Racing Applications:

• Drag Racing
• Drift
• Road Racing
• Rallye
• Pulling
• Circle Track

Every SPEC clutch kit and flywheel is SFI approved, ensuring compliance with sanctioned racing event requirements. The SM664 is the go-to choice for competitors who need a lightweight, high-response clutch that can handle the demands of a seriously built engine.