This problem is totally baffling me. I've been working on cars for over seventy years but have never run across this before. I have a 1974 Duster, 318, power disc brakes, Edelbrock 4bbl (but this problem was there prior to the 4bbl conversion). My brakes have absolutely no feel in the pedal what-so-ever. The pedal feels like it's not connected to anything. About halfway down, the brakes go to full lock. After trying everything I could think of, I spent a pile of bucks to have a "pro" fix it. New shoes, new pads, new master cylinder, and a new vacuum booster and it's still the same. Does anybody have "first-hand" experience with this kind of problem?