3/4" UHL x 3/8-16" (Set Of 12)

PR66751

66751

Fits: GM V6, SB 265-400, Buick, Olds, Pontiac '79 & earlier Mopar BB 383-440 exc 413, AMC V8's w 3/8" bolts Each PROFORM 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, PROFORM Header Bolts can be untightened with a normal wrench, lubricated, and reused.