Front disc brake dragging (and locking up)

[jeromio]

Background: I have a 66 C10 with a McGoughy's front disc kit. Pretty sure this uses D52 calipers and corvette rotors. At any rate, the calipers are new, rotors new, hoses new, brake lines new. I am using a 97 Fbody (camaro/firebird) booster and master cylinder (and an LT1 from the same vehicle). Also a Wilwood adjustable proportioning valve. I have the 97 rear calipers with Impala SS rotors.

I did the front discs first. After a couple days of driving it, the fronts locked up completely. Weird. Ok, so I figured it had to do w/ still having drums in the back. I could drive it around and eventually the pedal would firm up and the dragging would get bad and I would have to "vent" the fluid pressure by just loosening a bleeder.

Then came the rear disc swap. No real change. As an aside, I'm not getting full braking to the rear - prop valve is wide open and rear brakes barely grab.

BUT - the major problem is this front drag. Here's a list of things I have tried:

- adjust rod all over the place. The pedal never comes close to touching the bump stop. I can max this thing out (shrink it) so that the pedal has to go to the floor to get any braking. No discernible difference in this drag problem

- Move pivot point 1 inch lower on pedal arm. Again, no difference

- Replace Master Cylinder. Rebleed everything.

- Replace MC with a more expensive one (again, rebleed)

- Check fluid level - make sure it's not too full.

- periodically jab HARD on the brakes

- Drive for a few days consciously pulling UP on the pedal with my left foot

I got nothing. I am tapped out. I do not get it. I can sometimes go a week of driving - 100 miles or so - and it all seems fine. Other days I have to vent pressure 5-6 times in a day. Or I'll feel the pedal firm up, vent, drive a few blocks and it firms back up! No rhyme nor reason.

Any ideas?

[PGSigns]

Almost sounds like a bad hose. I fixed a motorcycle a couple of years ago that the brake fluid swelled the inside of the hose and caused the rear brake to drag.
Jimmy

[jeromio]

Hm. That would be a possibility. But, the hoses are new and they look good. They came with the kit so I am presuming that they aren't getting kinked or otherwise malformed with use (turning, suspension travel, etc).

[PGSigns]

Thats the only thing I can think of unless the master cylinder you have has residual pressure valves built in and they are bad.
Jimmy