Brake Problem

I'm installing new brakes. I've done the A-body junk yard conversion. I bled the brakes. Probably pumped a gallon through altogether. It's all fluid coming through, and no leaks anywhere. The problem is, first push of the pedal goes all the way to the floor. If I pump them 3 or 4 times, it's solid as a rock. I'm using a prop valve from an 80 something Aspen. Same as the brakes.

I plugged the rear reservoir and left the front line(rear brakes) hooked up. Solid as a rock. I did the reverse, plugging the front and I get the problem. So, it appears there's something in the front. So I bled the front again and pumped another bunch through. Same deal. First pump goes all the way to the floor. After three or four pumps, I can hold them hard for as long as I want. I can even release the pedal about half way to 3/4 out. Still solid as a rock. But, the minute I let the pedal all the way out, I then lose it until I pump them up again.

Any suggestions?