Front Brakes "sticking"

I am refurbishing a 1985 Mustang GT that was used in the SCCA American Sedan class from 1990-95. It is a gutted, "climb in the window" race car. I've not raced it in the Vintage events yet. I have used it for about 400 miles on the street (cruise nights). It has NJ Collector Car inspection and plates and is limited mileage street legal.

The front brakes are the OEM FoMoCo and the rear disc brakes are (seller told me) a Ford Racing conversion kit. The Master cylinder appear to have been replaced and may have been part of the rear disc brake conversion kit. The proportioning valve appears to the the OEM 1985 (disc/drum) but I am not positive it is.

The front brakes "drag" or stick after the car is driven and warms up completely. This problem existed as soon as I got car on the road. I found and replaced a frozen RF caliper thinkng the problem was cured. I replaced both front calipers w/rebuilt units at that time.

When the car is cold, the front wheels spin freely as do the rears. Only after the car warms up does the problem arise. I drove 10 highway miles yesterday directly to a garage with a lift, raised the car and both front wheels could not be turned by hand. After letting the car cool down for an hour, the front wheels spun freely again! The rear brakes never stick and always spin freely.

This problem is so bad that from 20 mph down to 0 (while coasting), the car will stop itself as if a ghost was stepping on the brake pedal!

Could header heat on the stock location proportioning valve be causing this? Could the proportioning valve be for disc/drum and not the right one for 4 wheel disc brakes? Could the proportioning valve be defective?

The brake fluid is clear as bottled spring water and nothing is leaking. Although I plan on eventually replacing the proportioning valve with a brake bias valve, I'd like to fix this problem first. Keep in mind that I'm assuming the valve is the culprit. Any ideas would be apprectiated.

Thanks

I replaced the front wheel bearings and seals with new ones when I did the calipers. It is definitely not bearing related, it's in the front brake hydraulics, like a sticking residual valve or other related issue.

Are the residual valves built into the Master Cylinder or the Proportioning Valves?

I replaced the brake hoses with brand new stainless braided hoses when I installed the new calipers. I also replaced the rear hose with a stainless unit.

I may just remove the OEM Proportioning Valve (FoMoCo calls it a Pressure Metering Valve) and plumb in a new, adjustable brake bias valve. The dealer gets about $120 for a new Pressure Metering Valve and an adjustable brake bias valve is a lot cheaper and I planned to go this way anyway. I'll just be doing it sooner than planned.

Are the residual valves built into the Master Cylinder or the Pressure Metering Valve?

Thanks,
Mark

Found the problem courtesy of ECI Hot Rod brakes in Connecticut. I used their "under-the-floor" Master Cylinder and Brake Pedal set up on my 1940 Ford Tudor Sedan Streetrod. I gave them a call asking for their advice.

After checking for some pedal "slop" to be sure the Master Cylinder wasn't preloaded by the pedal rod. I found the Proportioning Valve is too close to the headers. When the car gets warmed up, the Proportioning Valve gets hot, then the brake fluid gets hot and it sticks the valve. I made up a "quickie" heat shield, drove the car on the highway for 20 minutes and the sticking disappeared completely.

This is happening because my new crate engine has GT40 heads and required a different header. These GT40 style header tubes come much closer to the Proportioning Valve and lines that go from it to the Master Cylinder.

ECI suggested eliminating the Proportioning Valve completely. It is not required for 4 wheel disc brakes. Plumb the brakes directly to the Master Cylinder, keeping the lines as far from heat as possible. Also, there is no need for residual valves due the Master Cylinder being higher than the brake calipers. They cautioned me to put the "T" in the front lines so as to have equal or nearly equal length lines from the "T" to the calipers to prevent possible pulling under braking. They also suggested not using a Brake Bias Valve for the way I use this old "track rat" race car.