Fits: GM BB 396-502 exc 348 & 409 Ford 5.0L, SB 289-302-351W, Mopar 413

Each PROFORM Grade 8Header Bolt is permanently assembled with a pair of special washers. When the boltis 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 isblocked 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.