[Jrainman]

I am not familiar with that proportion Valve , but the standard P valves have a shuttle valve, the shuttle valve has the ability to shut off your front or back fluid pressure .this is designed for if a leak occurs (detected) , this is activated by your brake switch witch is wired to your Brake dash lite , So what happened in your case is when you bled the front you tripped the shuttle Valve , if you have a brake lite switch remove it from the P block look down in the block you should see a rod at the bottom of the hole , get a pick or small screwdriver and move the rod to the opposite direction from where it sits now ,this will open the port to your rear lines and you should be able to do your bleed procedure , There is a plastic device (tool) that you are suppose use , you are suppose to take out your brake switch and thread this plastic tool in when doing a installation as you are doing , this plastic device (tool) locks that rod in position so what you are experiencing does not occur. I find that all the brake conversion kits never have this in there instructions.