Here's the set-up: Original '68 4-wheel drum car converted to front power disc/rear drums; all new original parts installed (remanufactured booster and master cylinder, new stainless lines, drums, discs, etc.).

Here's the problem: Bench bled the cylinder, front discs worked fine, but no pressure to the rear drums. Replaced the cylinder, bench bled the replacement, still no pressure to the rear.

The solution: We have no idea (other than air in the lines, which we're working on). Any other suggestions??

Proportioning valve maybe?

When you replaced everything, that included the rubber line above the rear end right? I know those can swell shut.

Other then that. Just keep trying to bleed it. Open a bleeder, and slowly pump the pedal.

Verify that the master cyl and pusrod length coming out of your booster is correct. There is a "long" pushrod for the deep hole master cyl, and a short pushrod for the shallow master cyl.
On the left is the long 4 inch pushrod, On the right is the 2 5/8" short pushrod, a difference of 1 3/8". Note the O ring to seal vaccum.

http://ourworld.compuserve.com/homepages/David_Pozzi/boosterpushrods.jpg

I recently did the same upgrade and changed the front to rear line as well. Not sure if this is your problem or not, but it takes a LOT of pumping to get that line filled back up with fluid if you're using the old pump and hold method. I'd say on the order of 25 or 30 pumps. Does the fluid level in the rear reservoir of the Master drop at all after you do 7 or 8 pumps in the bleeding process? If yes, you probably just need to keep bleeding. If the level doesn't change, you may have a different problem...

What part of Houston are you in? I'm in the Tomball area...

Scott

Thanks guys for all of the good advice! It's definitely not the pushrod, but I plan to check the rear-end rubber line and proportioning valve as well as try the "pump and hold" approach on Monday. I'll report back when we get it figured out.

BTW Scott, I'm on the other side of the "world"--Sugarland. Thanks for your help.

Chew, chew, chew, I'm eating my words! I was certain that the rear brake problem was not being caused by the booster pushrod. Boy was I wrong! Just got done grinding 1/4" off the rod, and the rear brakes work fine now.

Special thanks to David P., and next time I promise to follow directions!

Thanks for posting back.
The booster link to the pedal should fully extend to limit upper pedal travel. if something else like the brake light switch is limiting pedal height, you need to correct that before working over the booster to master cyl pushrod length.
There is usually some adjustment in the clevis.
David