This is for my '32 Ford Roadster with the MC/power booster mounted in the brake. I've been chasing down a shitty brake situation for weeks now and I'm waiting for an adjustable proportioning valve to install as my last piece of the mystery problem. So far I found a master cylinder that was leaking at the bore end, nine really bad brake line ends, and a poorly adjusted power booster rod. So I replaced the master cylinder with a 1.125" bore GM (Corvette) master cylinder, new 7" power booster, all new nickel copper 3/16" lines, new Wilwood residual valves, new front caliper, new stainless braided front brake hoses, and I even replaced the front brake pads and scuffed the rotors in case they were glazed from previously getting hot. I've put it all together, used a Motive pressure bleeder (then manually bled them) but I can't get the brakes to really grab unless I preload the master cylinder with the power booster rod so I believe I need to lessen the pressure to the drum brakes so the disc brakes receive more pressure from the MC. I've attached a drawing. Thoughts please!! (again) View attachment 4385570
The bigger master reservoir serves the disc brakes. Are you getting enough vacuum to run the booster? What size master bore did the front brakes originally have (you didn't tell us what the caliper came out of)?
I didn't do a vacuum test but it's coming right off of the rear of the carburetor and it appears to be working. The previous master was 1" bore but I couldn't find a local retailer who had a 1" bore so I bought this corvette MC.