I have a 67 Elcamino that I'm doing complete drivetrain swap
in the garage. 327,turbo 350, 12 bolt
HERE'S THE PROBLEM!

I got the engine and transmission installed, went for short breakin
drive with open headers. brakes worked good. brought it back to the house. up on jack stands. removed old 10 bolt rear, took 12 bolt to have gone thru completely. Sat 1 week, Put in 12 bolt, installed new wheel cylinders, shoes, hardware, bleed brakes, lots of air. adjusted rear shoes twice. Rear brakes will not lock up. bleed twice more. checked for pinched lines, none found. when I did engine swap I had to move
proportioning valve to new location. so headers would clear.
I'm leaning towards master cylinder. I did bleed fronts and they do
lock up. pedel seems to be going down to far no matter how much I
bleed or adjust. FRONT BRAKES ARE CONVERTED DISC SETUP
THANKS JAY

Did the front disk kit come with a proportioning valve? Adjustable? You can't use the stock drum/drum valve on a disk/drum setup. Although what happens when you do is usually the opposite situation of what you have - the rears will lock up first.

If you have a brake pressure gauge, make sure your getting 300 psi to the rear lines, that's what your drums need.

Other than that we're guessing - but a possible start would be to look at why the pedal goes down too far. Most obvious is there is still air in the system. Second, is the clevis in the proper pedal hole for your setup? (manual top hole vs power on the lower hole). Then I'd check the MC or booster push rod length. Do a search here and you will find there are a couple different sizes. Too short of one will also cause the pedal condition you have as well as not pushing the piston far enough to get enough pressure to the rear.

Start with the free & easy before throwing parts at it! you'll find it.

i WILL PULL MASTER CYLINDER OFF AND BENCH BLEED IT SUNDAY
BUT WHAT GETS ME IS THEY WORKED GREAT WITH 10 BOLT AND QUIT
WITH 12 BOLT. NEW PARTS ARE SHOES, WHEEL CYLINDERS, RUBBER BRAKE HOSE TO THE DIFF. THE REST OF THE SYSTEM WAS IN PLACE WHEN I BOUGHT IT 2 YEARS AGO..AND ALWAYS WORKED GREAT
THANKS JAY

STILL FIGHTING THIS BRAKE PROBLEM...BLED AGAIN, BENCH BLED OLD MASTER , NO LUCK, PUT ON NEW MASTER..REBLED SYSTEM NO LUCK
TOMORROW I'LL PULL OFF P-VALVE TO INSPECT AND WHO KNOWS FROM THERE. BEEN WORKING ON CARS FOR MORE YEARS THEN I CARE TO THINK ABOUT AND THIS ONE'S KICKIN MY B___! TOMORROW'S ANTHER DAY.
THANKS JAY:confused:

]BRAKE PROBLEM SOLVED!
Well i finally have rear brakes. I replaced about every thing on the system and it still didn't work...used over 2 qts fluid. bench bleed..the works
A good friend told me to try something and it worked
I put the rear diff as high as my 7 ton jack stans and jack would go..about 30 inchs
under the bumper to floor... left front tires on ground...opened master cylinder and rear bleeder valves and ran fluid thru for about 2 hours..then rebleed again and I FINALLY
GOT REAR BRAKES! Took for short drive that 400 hp 327 runs good gotta
clean her up for car show Friday nite. fine tune carb and adjustment still needed and hope i fixed small oil leak I found BJ"S happy she can drive her car soon

THANKS FOR THE HELP. JAY AND BJ

I guess that did two things, leveled the MC so you could 'bench' bleed on the car as well as raise the rear bleeders up to help knock loose any trapped bubbles. I had a heck of a time getting my rears bled - I ended up with a 'garden sprayer' style power bleeder.

MJRIBEIRO, which garden sprayer pressure bleeder did you get?

Did it work well, and can you use it yourself?

I do most of my stuff by myself, and was thinking it would help.

Thanks.

I HAVE A FRIEND WITH 49 STUDEBAKER PU THAT i'M HELPING WITH HIS BRAKES TOMORROW...ANTHER FRIEND LOANED ME HIS AIR BLEEDER TODAY.
WILL TRY AND LET YOU KNOW HOW IT WORKED...HOOK UP TO SHOP AIR AND SUCK FLUID THRU. SEEN HIM USE IT TODAY..ABOUT 1 QUART FLUID IN 5 MINS.
DON'T NEED HELP TO USE JUST HAVE TO WATCH FLUID IN MASTER CLOSELY
JAY

MJRIBEIRO, which garden sprayer pressure bleeder did you get?

Did it work well, and can you use it yourself?

I do most of my stuff by myself, and was thinking it would help.

Thanks.
Its a 'Motive' brand.

Just make sure you get the one with GM MC adapters

http://www.fcpgroton.com/product-exec/product_id/22523/nm/Motive+Power+Brake+Bleeder

Studebaker brakes are good took us about 15 mins to flush complete system
The bleeder I used was a MITYVAC. really easy to use
jay