Each PROFORM 12.9 Steel (equiv. Grade 8+) Header Bolt is permanently assembled with a pair of special washers. When the bolt is torqued to 28+ ft-lbs, the washers super-hardened external teeth bite into and grip the bottom of the bolt head and the top surface of the header. After being self-locked in this manner, any bolt-loosening rotation is blocked by a wedge-locking action created by the washers interfacing, matching cams. It's an uphill climb: vibration that might ordinarily loosen the bolt actually increases the wedge-locking tension, securing the bolt even more. Because this simple wedge-locking method uses tension instead of friction, contact with oil actually facilitates the wedge effect. When changing headers, PROFORMHeader Bolts can be untightened with a normal wrench, lubricated, and reused.

Features:

• Grade 8 (12.9) Steel
• Hex Head Type
• 1-inch Length
• Fits GM BB 396-502 exc 348 and 409, Ford 5.0L, SB 289-302-351W, Mopar 413
• Sold as One Set of16 Pieces