I have completed the drum to disc conversion. Put in a borg warner 9 with the old style calipers(my first mistake after reading post history) I bought it used and rusty with master cyl and prop valve. I put rebuilt calipers on and new pads installed the master etc. Now I have to pump it up to get slowed down. I bled them numerous times and made sure the E brake is adusted and holds. Brake stand will melt down the rears, which is cool but not comforting knowing that car will carry wife and son. Did I get the wrong prop valve...or should i bench bleed master cyl??or is this normal for the old cast rears??? I know the ultimate answer is alum style calipers but I already have bout 400 bucks in this mistake already!

86 Z
crappy borg warner 9 ....didnt do my research
75 4bolt 355

Was a new Master Cylinder installed or the old one?

the rearend was bought with the master cyl and prop valve used package deal. I think ill go with a adj prop valve in the rear line and a blank tee in front???

The front brakes do the majority of the work when stopping, so I don't think you put all the blame on the rear calipers. When you say the Master Cylinder you currently have is used — how used? Do you now how long it was sitting around before you bough it?

If anything, you might want to start with a new Master Cylinder.

Did you bench bleed the master/ new valve?

no, I will bleed the original master install it and see how it turns out.....Thank you

Ahh the joys of old style discs! I remember not being able to put my old car in park on ice because even while stopped the rears would keep spinning at idle! I remember reading about those calipers too in various posts , and I think I remember some even saying that the rebuilt ones were a lot of the times junk too. You probably spent a bunch of money on new ones, but I'd consider just doing an LS1 swap. I bought the whole setup for $150 on ebay, and it was relativley easy. At least then you have a proven design without the stupid e-brake-built-in calipers. Just my two cents.