Testing a Proportioning Valve?

trapster said
I am afraid that riding the brakes is just causing the rear drums to fade enough that they do not lock up anymore. this cannot be good for them I think we just need to add or adjust the rear proportioning valve.
something like this Classic Performance Brake Proportioning Valves PV-2 or Right Stuff Detailing RMB6801

The first one is what you need, not the second one. Or just this

Summit Racing® Adjustable Brake Proportioning Valves SUM-G3905

The problem with the stock style prop valve is all the fittings are different sizes, so you can’t mix up the lines. On a drum/drum car that has a distribution block all the fittings are the same. So you either need adaptors, new lines, or reflare the lines with new fittings. But the lines aren’t all the right length either going from a distribution block to a combo valve.

So it’s a ton easier to add that in-line adjuster into the rear line than replace the distribution block with a combination valve

Mattax said
it could just be the disks and the pad material. I had (have) some Cyclpro - Chrysler pads that didn't have a lot grab or pedal feel - especially with a disk that's worn smooth. Or the calipers aren't working. If it feels like the front, I'd focus on the front.

Rear brakes help the most on the initial and light braking inputs. While under hard braking weight shifts forward reducing the traction of the rears. That's when the proportioning valve is needed.

As far as heat goes, with street use, you will have to try really hard to heat the linings to a temperature where the friction declines. A really long steep downhill in the mountains might get there if riding the brakes. That's true both for the fronts and the rears. In fact their performance may increase slightly after a couple applications in a row.

Also a good point. Could also be the front pads are just contaminated. A little grease will ruin those things for a long time. Or improper break in and they’re glazed over.

If either of those are possible you can sometimes “resurface” the face of the pads with some sandpaper (do not breathe that crap!!!). Then try again on the break in.