The Stovebolt Site Forums The Shop Area The HiPo Shop disc brake problems

Hi, I have disc brakes up front and drums in the rear of my 52 suburban street rod, and I have been having issues getting them to work right. The from brakes came with a Mustang II kit from fatman (they are Gm calipers and ford discs). I am running a dual master cylinder/booster designed for a disc/drum combo and an adjustable proportioning valve from wilwood.
Everything in the system is brand new. I initially had a spongy pedal after bench bleeding and bleeding the entire system multiple times. So I ajusted the pushrod on the booster and the pedal firmed up... but later developed brake drag after driving for more than 5 miles. So I backed off the pushrod, to once again have a spongy pedal. When I plug the ports in the master cylinder the pedal is completely stiff, so I don't believe there is a problem with the master cylinder. I have checked the lines for leaks, and the level in the master cylinder does not drop, so I don't think that is an issue. I have also bled the system problem 15 times, both with the two person method and with a vaccum unit running off of my compressor.
Today I decided to plug just the rear port and the master cylinder and then also just the front port. When plugging the feed to the front brakes the pedal was stiff. But when nearly to the floor when plugging the port to the rear. This leads me to believe that the problem is with the front brakes. So I put a tube on the front brakes and had my dad push the pedal in with the bleeder cracked. No fluid came from the tube until the pedal was nearly to the floor. Does anyone know what could be causing this? Like I said, the pedal was almost instantly stiff with connected to only the rear brakes. Its like the two ports in the master cylinder are activating at two different times. Any help would be greatly appriciated. thanks