How close would you guys let your header be near your brake porportional valve?

Mine has about... 1/16 - 1/8 inch... any closer and the tubes will touch against the tubes...

I had that concern when I changed to the Hooker headers and relocated mine. I don't know if it would have been a problem or not, don't like to take risks with brakes or suspension. "The Right Stuff" makes a kit to relocate the p/v just below the master cylinder.

Dan, do you have any links for "The Right Stuff"?

On my 67, I put a Delco combination valve (71 Chevelle style)in the same location as my original distribution block, down on the framehorn about 3 inches from the header tube. Within 1000 miles, I started having problems with rear brake lockup. I bought a pressure gage and found the line pressure front and rear to be equal at about 1100psi. Bought a new combo valve and mounted it on the master cylinder, and my brake pressure at the rear dropped to 500 psi. I'm convinced the heat fried the first combo valve.

http://www.rightstuffdetailing.com/

Had this problem on a 69 that we dropped a 454 in. We tweeked the bracket that holds the distribution block and it seems to be fine. The headers don't touch it now.