My friend has a 71 Challenger 412/340, 727 with Gear Vendors . He recently upgraded the front disc brakes to use the 2nd gen Viper 4 piston aluminum calipers while keeping the 11.75 Cordoba rotors. To do this, he installed the correct 70 B-body drum brake knuckles and the caliper adapter brackets from AR Engineering. Everything fit together fine. He had a later model 2 bolt aluminum master cylinder with the remaining brake lines and proportioning valve that came on the car. Braking was fair, but no better than with the single piston calipers. The WIERD thing is that while braking in a turn, the brake pedal would push back toward his foot! He changed to a different M/C with the same symptom still there. I told him to check the wheel bearings. He did, and the nut was loose by 2 1/2 turns on one side and about 3/4 on the other. A test session afterwards showed no change. The brake hoses are not binding. He added a Wilwood adjustable prop valve since he knew it was a good idea, not in an effort to cure this problem. With the current setup, it stops better than before, but the pulsating upward from the pedal during turns still has us confused. Okay now, any clues?
. I'd jack up the front/remove the wheels and have a helper play w the pedal as something has to be loose/excessive play that's causing the pistons to be pushed back during the lateral movement in the turns. Start w the bearings