Brake upgrade problems - need help

[CreepinDeth]

I have a 1970 Olds 442 clone.
I took out the fake Olds 12 bolt 2.78 rear end, and put in a Chevy 12 Bolt Eaton Posi 3.73 I got off another member here earlier this year. It came with the Baer rear 11" disc setup. I have stock 10.75" factory front disc brakes.
https://static1.pt-content.com/images/pt/2010/07/Olds12BoltDiscBrakes2-1.jpg

I was told a 1979 Corvette Master with the 1 1/8" bore would be a great addition to make this system work. Plus an Adjustable Proportioning Valve for the rear. So far I've bled the system 5 - 6 times and I still have a mushy brake pedal. I put in a Fenco rebuilt 79 Vette master with 3/16" front and 1/4" rear lines. I'm not exactly sure if I need to upgrade to a 1" bore master cylinder, or if I'm doing something wrong here.

No matter what I have done, I still have an ultra mush pedal and I know I don't have any air left in there. I checked everywhere for leaks too, nothing. Something else has to be the problem. I was hoping maybe someone can help me figure it out. :willy: So far I've been told my rebuilt master COULD have bad seals, to order another. I just want to be sure what I'm putting in is going to really work. I've see other guys upgrade to rear discs with this master with no problems.

I have no idea if this Baer brake setup uses a big or little piston and how I should calculate this all out. I'm stabbing in the dark here.

[ProdigyCustoms]

Just because the master is rebuilt does not mean it was do properly. lots of problems with parts store rebuilt masters. Try another.

[Ron S]

Is it manual or power brakes? If it is manual, you should be running a 7/8 master, made that mistake myself, almost kissed the wall because of it. I've always used 3/16 line front and back, don't know if that make cause a problem, but pedal pressure will be less and more firm with the smaller piston size and line. Usually the power brakes will require a bigger bore. I was taught this by Todd at Baer and Payton King could right a book on braking systems. Ron

[CreepinDeth]

Power brakes, 11" booster. This is a family cruiser. Nothing crazy.

I bled the master, but I didn't plug it when I was installing it.
Plus I had to make some flared fittings while it sat there unplugged.
Tobin told me it's possible it's gotta be bled again or the MC could be bad.

I will try bleeding the MC again.

[406 Q-ship]

Bigger bore on the master cylinder will move more fluid at the expense of pressure. I would switch down to a master cylinder from a manual brake Corvette from 65 to 81, they are 1". The higher pressure of the 1" should bring back some pedal feel.

[CarlC]

There's a serious mis-match of caliper piston bore areas. Likely no matter what you do it won't be a well balanced system.

The stock caliper works well with a 1-1/8" MC and assist. The Baer/4th gen Camaro LT1 caliper needs a 15/16" bore MC and assist. That's a huge difference in effective working area.

[paul67]

are the bleed nipples on the top of the caliper as i could not see them in the pic.Also does the pedal go hard on the second pump.

[Mr. Anderson]

You probably have, but just in case...when you bled the system, did you have the proportioning valve adjusted wide open?

I've had customers bleed with the valve turned down and never could get the air out.

[MrQuick]

are the bleed nipples on the top of the caliper as i could not see them in the pic.Also does the pedal go hard on the second pump.
yeah might be up side down, cause I believe the parking brake bracket is on the bottom of the assembly.

[prostreet69camaro]

Carl is right. Baer uses a 15/16" master cylinder. I have all baer brakes and a 1" would not work. Changed to the 15/16" bore and my brakes are fine.

[406 Q-ship]

Carl is right. Baer uses a 15/16" master cylinder. I have all baer brakes and a 1" would not work. Changed to the 15/16" bore and my brakes are fine.

Funny, Baer is who told me to use 1" bore master.

[cornfed]

Photo is of the left/driver's side wheel. The caliper and bracket are on the wrong side of the axle. Recently I installed the rear Baer kit on my MCSS 7.5" axle. Caliper was at 4 o'clock which places the parking brake mechanism at 6 o'clock. This assumes mounting for the 12-bolt is same as the 10-bolt.

Also in my instructions for G-body using the stock master with adjustable prop valve, are directions to remove the rear axle valve inside the prop valve.

[prostreet69camaro]

Funny, Baer is who told me to use 1" bore master.

When I had the 1" bore master it seemed like I just ran thru the brakes. I went to the 15/16" bore and now it stops good. Between the 2 sizes is about 300PSI.

How does yours work with the 1" bore?