I have read numerous threads on here about rear discs. And about a million different ideas and ways to accomplish the task.

I've got the hardware all sorted out, good to go. What I need the skinny on is proportioning valves. I know the stocks valves incorporate the residual pressure valve for the drums. I know some people leave them in. Where as others remove them completely, hard plumb the front brakes with no prop valve and install an adjustable prop valve going only to the rear.

In the interest of doing it this right the first time, can anyone give me a clue on plumbing this setup? Or what worked for you?

Thanks guys.

And the truck in question is my sig truck.

I just plumbed my front MC port to the front brakes and the rear port to the rear.....with an adj. prop valve in line to the rear. Adj the rear until they just about lockup under hard braking....or to your liking.

on the blazer i ran no prop. valve and it worked perfect, but know other people who had to run an adjustable valve.

stock with no issues in braking power.


i did have one freeze up and not function but it was left open and unused for nearly a year.

I bought an adjustable proportioning valve, but didn't install it. I figured I would try it without a proportioning valve first. Mine work great just plumbed directly to the front and rear. I think a lot has to do with the amount of weight you have over your rear axle. In a pickup, you may need the valve.

I just did this mod when i swapped a 14FF into my 86 GMC 3/4ton All i did was use 75 chevy 3/4 ton calipers and rotors and that was it. I did not mess with the master or the valve. I dont have anymore drag on the rear rotors then fronts would. And after a few test stops and a hard stop i find its just right..

Shoots, thanks for the responses...my friend has a brand new wilwood adjustable prop valve still in the box that he wants a 4 pack of Boddingtons for...

So I guess I will give it a swing this weekend, and let you guys know how it goes.

Thanks for the help.

mine is all stock 87 blazer parts till the rear disc conversion and it works pretty good right now, no lock up or drag.