Heat causing caliper rub?

I'd say that is exactly what is happening.
You might try some high-temp header wrap.

ULTRA HIGHTEMP WRAP

I have the headers coated with Jet Hot. I always hear horror stories about header wrap rusting out headers. What if I fabbed up some aluminum heat shields either over the lines of mounted to the headers?

The wrap will definitely rust out the headers much faster than normal. The Aluminum heat shield would definitely help. Perhaps you could wrap your Brake lines with this: Heat Shield Wrap

It's supposed to reflect up to 95% of the radiant heat.

You could also cover your heat-shield with this
Lava Mat, volcanic rock heat-shield. LAVA HEAT SHIELD

It looks pretty trick and it would improve the performance of your proposed heat-shield.

I think your assessment is bang-on. I also think you will need a much more effective heat shield than the thin stuff you have, especially since the heat can soak around the small pads you have on the bottom of the masters.

The header wrap should help a lot but you might not like the bandaged look. Coating inside and out will obviously help too, but I suspect you will need a cocktail of solutions given the proximity to your brake lines/masters to your high-heat headers. Have you considered an aluminum heat-deflector plate under the masters and mounted to the firewall? I'd do the same between the lines and the headers (sort or a small double firewall).

I had my GT40 headers wrapped and it does speed rust.

Have you ever noticed any changes in your clutch take-up? One would expect it to be similarly affected.

Mark

I was thinking about making a heat shield out of aluminum that mounts to the header and "boxes" the top and side of the header that faces the brake lines. I kind of "L" but would need to find a clamp that I could put around the header to minimize rust (even though they are coated).

My first thought was to check your MC push rod length. This is a standard problem with new MC installs in our Panteras. Just a little too tight, heat things up, and now you have partial push rod movement.

As for a heat shield, aluminum is a GREAT heat conductor. It will soon radiate off the back side whatever temp is hitting it on the front side.

Stainless is not a good heat conductor and would serve you much better.

Get a flat sheet of stainless sheet. Make it as wide as the space your 3 MC take and deep enough to extend out far enough from your MC fire wall section to cover the header pipes. Add a 1/2" 90 degree bend on the fire wall edge and attach it to the fire wall.

Larry

Stainless it is!

Khan,

If your brake master cylinders have what are called "residual check valves" in them, then this could be the reason for the brake "drag" when hot.

The residual check valve causes a small amount of pressure (~2 to 5 psi) to be retained in the brake lines when the brake pedal is not depressed. The brake fluid in the lines heats and expands, but the residual check valve allows any excess pressure that would have built up in the brake lines to be bled back into the master cylinder.

Let's say that the check valve has a rating of 2 psi. This means that the max pressure that will be present in the brake lines will be 2 psi (when the brake pedal is not depressed).

As the brake fluid heats and expands from whatever heat source (engine, exhaust, brake pad friction....), the check valve will only allow 2 psi to remain in the brake lines. When the engine is shut off, further heating to the brake fluid may occur due to the engine's "heat soak". But the max pressure in the brake lines will only be 2 psi.

When everything cools, the brake fluid contracts, and the pressure in the brake lines drops below the 2 psi check valve rating.

This may not be the cause of your brake drag issue. Just the normal expansion of the pads, rotors, and calipers caused by normal braking will cause some drag when hot and less drag when cold.

A heat shield certainly won't hurt and it may solve your issue. You might try a temporary heat shield held in place with straps (of some sort) as a test before fabricating a nice clean sexy looking permanent one.

John

Good point, JB. Some residual pressure valves are built into the master cylinders and some are in-line. If you have the wrong valve for the application, it certainly will cause drag. I arbitrarily remove them. A marginally misadjusted MC brake activation rod from the pedal will also do it: if the MC piston is adjusted too far forward, the return port in the MC is blocked and every time you hit the brakes, pressure will increase a little until the rotor stops turning. This can also happen with system heat expanding things. Is the problem both front & rear brakes or just on one end?

some in the front but seems to hit the rears more (they have seperate MC's)

The heat shield would be a good idea but if it was mine I’d check the master push rods first. Expect yours should have no preload and a smidge of free play just to make sure the pistons are returning all the way.

Mike