A dual master cylinder. The last time I bled my dual master cylinder with the drum brakes the brake valve shifted and cut off the side I was bleeding out and the pedal felt tight and would not go down. I finally had to open one of the rear bleeders and one front to get the pedal to push down to move the piston in the M/C. Is there a way to bleed just the front? It seems as if the brake valve is doing it's job if I open the front bleeders and the pedal wont go to the floor. I have just converted to a Granada disc and I have to bleed the front so I would like any help before I start.