Rear Brakes Won't Bleed?

[Kisner]

Update - my luck finally changed and after 3 days of soaking in "liquid wrench", the brake line nut broke free and I removed distribution block. Thought I'd experiment and remove end nut and see if I could grab hold of end of piston and pull the proportioning valve back to the center position. After 2 hours and 3 pairs of tweesers (only thing that would fit in the end - squeezed them with my needle nose plyers), was able to forcefully pull the valve back to perfect center position. Cleaned it up with fine steel wool (was painted black over the years when they painted the engine compartment) and now it's brialliant , shiny brass again. Cleaned it inside and out - B=brand new looking just like it was in 68. Now to see if I can get a refund on the one I already ordered.