HELP! Can't bleed brakes and the front disc lock up

[Canonman67]

So I'm winding down the build and trying to bleed the brakes so I can get it on the road. It's a '70 F100 flareside with a dana 44 sporting 1 3/4 drums and shoes on the rear with a Scarebird conversion on the front (Chevy calipers, Dodge rotors). The master cylinder, booster, differential and metering valves all came from a '71 camper special with disc/drums. I've bench bled the master cylinder and get fluid at all four corners. The pedal feels like it firms up but then you are able to push through usually ending up about an inch above the bottom of travel. It only takes one pump to lock up the front disc and the only way to relieve them is to crack the bleeder. I checked the differential valve and it seems to be stuck in the center so I'm assuming (I know, I know) that's not the problem. I'm stuck and can't find anything in my searches that addresses my issues. Any ideas? Thoughts? Thanks in advance.

[Canonman67]

So it appears that my sticky disc problem stems from my not putting any lube on the slides. One down. Now everyone at the shop says the not bleeding issue feels more like the master cylinder. I was able to change that out before I had to head home to get ready for work. I'll keep posting here on my progress for future reference.

[Canonman67]

Had issues with the new master cylinder, the front fitting wouldn't seal no matter what I did, returned it for another one and I'm finally getting some pedal.



The front adapter was the problem. I still need to bleed the brakes since no one was at the shop to help me but at least I can pump them up.

[Ren]

Had the same issue on disc brakes years ago. Like you, I replaced the master cylinder. I know it sounds strange, but the problem was solved by replacing the rubber brake lines with new ones.

[Canonman67]

No I could see how they could collapse on themselves. Since I've already replaced them I hope I don't have to buy them again. We'll see next week when I have help to bleed them.