I an not an expert but I think there may be some wrong info in the above posts. I am sure that for a disc setup you will need a 2 pound residual not 10. Some master cylinders have built in residual valves, others do not. Gently insert a small dowel or tooth pick into the ports. If it goes in about 1/2" then the master clyinder does not have a built in residual valve. If the dowel goes in just a little then it does have the valve. Also, when the master cylinder sets low like yours, residual valves are recomended because your brake lines run higher than the master cylinder. I see no use in changing the size of your brake lines for the same type of set up. Do make sure they don't have crud in them. Good luck.

Six volt guy living in a twelve volt world