[Tom Goldman]

Tony didn't say what car he's doing this on ,or if he's using an OEM master cylinder .
Many older disc drum cars have integral residual valves ,either in the master cyl itself ,or in the factory combination/proportion valve that can cause excessive brake drag when being converted from drum to disc .
When making major system changes like this ,it's best to replace the master cylinder and the factory distribution block with parts that are sized properly for the application , particularly if the car will be foot braked .
On several of the Stockers I've built I've used Bias valves on the front brakes , not the rear,to proportion proper braking , especially at the finishline.