Dragula when I put Wilwoods on my Cuda in the late 80's I had the same problem. If you are using the stock MC there is a small pressure valve(that keeps a small amount of pressure on at all times for the drum brakes) that can be removed from the MC. I used a small screw put it into the seat(where the line for the rear brakes entered to MC)and wiggled the seat out. I removed the valve and bingo no more drag. I've had this set up since 1988. If you have an aftermarket MC not sure if this will help. Wasn't sure which MC you were using.