hi
im in the process of swapping my 9-bolt discs to a ford 9 inch drums.my question is ,do i have to change the proportioning valve or master cylinder to accomadate this swap???

If you're downgrading from PBRs, then it should be OK, as their hydraulic requirements are similar. Hiwever if you're upgrading from Saginaws, you'll probably need the right MC & PV, because theirs are considerably different.

You'll definitely need the drum brake prop valve, but the MC might work, depending on which one you have. I converted an 87 Firebird to rear disc, and was able to reuse the drum brake MC (but used a 1LE prop valve)...that was with the Delco iron calipers.

thanks for the replys
i dont know the difference between(saginaws vs pbrs).the old rear disc brakes had big ribbed aluminum calipers that had a plate with springs attached to the piston of the caliper(weird design).

if you want a disk/drum prop valve, you can have mine, i dont need it anymore. where in chicago are you located?

hi kag
im on the nw side of chicago.i was wondering what would happen if i used the stock propotioning valve(rear brakes lock up??)

The ribbed aluminum ones are PBRs, similar to what came on 93-97 V8 cars (and some later 6s). The other style, the Delcos, are cast iron (HEAVY!) and the calipers are mounted on opposite sides from each other (drivers side behind the rotor, pass in front of it).

i was wondering why you want to switch from disks to drums? isn't the swap usually the other way around? just wondering. i have discs in front and drums in back, should i keep the stock drums or switch over to a bigger slotted or cross-drilled disc brakes? thanks

2 reasons why i went to drums.
1.it was a cheaper option.
2.i have 15x10 weld rims in the rear.i had to grind my old calipers for rims to fit.

also id like to mention drum last alot longer than disc do.The rear brakes only do about 30 percent of the braking.

so you think i should upgrade the front brakes only and keep the rear stock drums? as a cheaper option i mean, because cheap is always good.

well i took my car to the track.tested the brakes and they were fine with the stock proportioning valve.

fastback
yeah i would leave rear drums alone.drums last twice as long then disk in the rear.You wont have a problem installing 15 inch rim with slicks on em.

why the ford brakes?

He's going to a 9" Ford rearend, most of which came with drums. This isn't an issue on aftermarket rears (Moser, etc) since they are set up to use the stock GM discs. For a drag application, though, the drums can actually be better, since you can back the adjusters off for less drag...cant do that with discs.