Hi everyone, My car is a 65 chevelle, stock 396/300hp

I recently did a booster change from a 9" booster that I got from MP Brakes(bulky for BB tall valve covers), to the original looking GM 9" booster(bought new repro).

So after the install, I went out for a test drive to see if I could lock the tires, like it used to do before, and it never skidded. So I come home and I look under the hood and see an old line kinda crimped, so I make a new one, bench bleed the M/C, and bleed all 4 corner. Take it out for another test drive, still won't lock up.

Before I took the car out for test drives, the car had a good pedal everytime. It didn't go to the floor, and it wasn't too hard.

So then, I unbolt the M/C(1" bore) to check the push rod. Everything looked good and I just had to install 2 washers each to have the M/C flat on the booster. I also made sure I tighten every flare nut and I bled them again just to be sure, and I found some more air, but the test drive is still the same results: Good pedal but doesn't lock up, it rolls to a stop. I even tried it in the pouring rain, still didn't lock up.

So now I'm thinking maybe the propprtional valve is out of adjustment, the brake pads and shoes could be glazed, there's still air in the system, or I need to go with a smaller bore M/C.

I'm stumped. Any help would be nice. thank you

-Eric

Oh and just to let everyone know, I did ALOT of searching but I never came across the right solution that worked.

Did you change the tire wheel combination?

Well I did switch to a taller tire in the front, 215 to a 225, but I didn't feel a loss of braking. I only started not locking up when I installed this GM booster.

Ok, I was coming back from work, and I finally locked up some wheels, BARELY, I think it was the front. I know my rear drums need adjusting, so I'll take care of that today, and reset the prop. valve.

I'll let you guys know after a test drive.

Ok, so yesturday I pulled the rear drums and found a leaky wheel cylinder on one side. Now I'm just curious on how long it was leaking for??? Something tells me it's not that that's causing most of my braking problem.

Today I'll buy a rebuild kit and hone the wheel cylinder, then I'll bleed it and if that doesn't work, I'll try adjusting the prop. valve, maybe I'll try that first before the wheel cylinder rebuild and see what happens.

I'll let everybody know, even though I'm probably talking to myself in my post, lol.

You should compare the price of the rebuild kit against a new wheel cylinder. Unless you are doing a concourse car the price of the new wheel cylinder makes it not worth whiled to spend the time rebuilding the old one.:waving:

Sounds good to me, thanks for the tip :)