Try bleeding it with out the proportioning valve....the valve is not always necessary depending on MC years and so on....If things don't work out I used a 75 non boosted corvette MC....you have to make a small adapter that bolts the 3 bolt MC to the fire wall....and you don't need a proportioning valve. But I love it, it was easy to bleed and I don't get any lock up and it has a great pedal feel.....But I would try taking your proportioning valve out first to see if you are able bleed them that way....I know you have new lines but you could always take them back off and blow air thru them to be sure something didn't fall into them somehow and clog the line a little....Good luck just some brainstorming ideas for you to try.....hope you get it fixed soon and easily.
