Odd brake problem on an Arntz/Butler.

[RallySnake]

I built my Arntz Cobra with Jaguar rear brakes from a XJ6. It took a little machine work on the mounting bosses to get them lined up on the XKE differential bracket correctly. On a recommendation from the Powermaster Brake people, I used a stock 1 inch single master cylinder and a remote vacuum booster. The front brakes are a combination of Chevy Monte Carlo rotors and Dodge Dart calipers as recommended by Butler Racing.

The car brakes very well for a few thousand miles. The problem is that after the rear brake pads wear down about one eighth of an inch, they simply quit working. I will find myself pushing much harder on the brake pedal only to make the front tires start sliding. I have bled the system with no effect. I have added a 2 pound residual pressure valve to the system at the master cylinder. But somehow, When the pads wear down to the same point, the rear brakes give up the ghost. There are no leaks anywhere.

I used a quarter inch brake line from the master cylinder to the brake booster and a quarter inch line from the brake booster to a 4 port junction. From there, I used three 3/16 inch lines, one to each front wheel and one to the rear. At the rear end there is a 3 way junction with 3/16 lines going to the calipers. I am thinking of replacing the line to the rear wheels with a larger one, but theoretically, that doesn't make sense. The pedal does not go to the floor and feels just fine even with worn pads. Replacing the rear pads always solves the problem for awhile. But my collection of slightly used rear pads is getting pretty large!

Any suggestions to solve this problem would be appreciated.