I have a 71 with headers. The proportioning valves on the brakes is in the stock position ( inside the frame). Yesterday, after driving around town for a couple of miles, the front disc brakes would not release. After massaging the brake pedal with my foot for 10 minutes ( the brake pedal was as hard as stone) The pedal finally loosened way up and almost went to the floor. Then the brake light on the dash came on. I suspect that the proportionig valve became over heated and would not let the front disc brakes release. The car is back in the garage for now. Should I move the proportioning valve? Where to? There is currently about a 1/2 inch clearance between the header and the valve. All components in the brake system are new/ factory rebuilt. I suspect I may need a new valve. Can anyone help me?

This does not sound like a proportioning valve to me (though if yours gets hot, I would suggest moving it, or shielding it from the headers with header wrap). This sounds like swollen rubber brake lines. When they swell, they act like a foot valve. They let fluid through because of the pressure you exert on the line, but very little pressure is applied in the reverse direction once the pad leaves the disc/drum. I've had 1 year old lines do this to me. Pull off your rubber lines and try to blow through them. It might just shock you.

If you think that heat is the culprit, put synthetic brake fluid in it and the problem should disappear as it absorbs heat better. The same thing just happened to a buddy's 56 Bel Air, had to wait for it to cool down before we could get it in the garage.
You could also have a bad brake hose, had that happen on my 70. The one caliper would not release pressure until I cracked the line open. I put new hoses on and problem solved.

if it is the brake hose only one of the calipers will lock shut making the steering wheel pull to that side. the heat will not only effect the fluid but the expansion of the internal parts in the valve. "the right stuff" sells the brackets and lines to relocate the valve up under the master cylinder. thats what i did and suggest doing that.

Saw similar problem on HP TV the guys moved Combo-valve more towards rear, I may have the same problem and that would really SUCK being that I already installed my ss brake lines and would have to cut, and lengthen appropriately etc etc etc

Thanks for the info. How do I get in touch with "the right stuff"? My rubber hoses are less than one year old. Is the problem in the material that they are made of? Would new ones help?

Also, both front disc brakes locked up. There was no pulling to the right or the left.
Thanks

the right stuff is at www.rightstuffdetailing.com (http://www.rightstuffdetailing.com)
1-800-405-2000. they have everything you need to relocate a new proportioning valve under the master cylinder away from the heat. graemlins/beers.gif