My buddies and I recently did a front power disk brake conversion from manual drums on my 67. I bought the kit from this guy, which included everything I needed...proportioning valve, MC, 9" booster, calipers, rotors, hardware...the works. However, I have to nearly STAND on the brake pedal to get the car to stop. The brakes have been bled, and there is plenty of vacuum for the booster (20). The pedal is very stiff, and like I mentioned earlier, it takes alot of pressure to stop the car.

I've contacted the guy, and he agreed to test the booster and to ship me a new one if the first one was defective. I wanted to run this by you guys before I have to pull the booster off the car, package it, and ship it out. Please help!! graemlins/clonk.gif

Ouch. I'm gonna watch this thread as I have this task coming up soon.

You have measured vacuum... was this actually in the booster line so that it is what the booster sees? I might pull the line and verify vacuum to the booster (cheap and easy :) ).

How is the check valve at the booster?

do you have the pushrod in the correct hole in the brake pedal?

Yes, I did check vacuum at the manifold and it is fine. The check valve's fine, too. The pushrod is in the correct place.

I've got a similar problem w/ my '64 Chevelle. I did a fr disc conv.,new booster,prop. valve, hoses, SS lines, rr 100% replaced new, the works!
Got the car on the road Dec.'04, all worked well about 2wks. Parked it 1mo. drove 2-3 wks, then noticed the pedal was very stiff. I checked the booster, fine. If I'm traveling 35-50mph,slowing quickly to stop at a light (not a panic stop by any means) the rear tires lock up. If I'm pulling out of my driveway I have to press HARD to slow or stop. I've noticed recently a smell of brakes from the rear wheels even after short distances. Due to an agravating hernea the last month, and having had surgery last week to fix it, I have yet to pull the rear drums off to inspect. But what could cause the brakes to act in this manner. The master is full, using DOT5, the pedal has little travel even while standing on it, it doesn't feel normal. :confused:

Maybe it's a Garden Grove phenomena.. graemlins/clonk.gif

Even if you have good vacuum at the manifold, it could still be a problem at the booster. I went through this with my Camaro. There should be a seal between the booster and the master cylinder, and those who have read mine and other people's threads about it know that not many people know about it.

Some say that it's not needed, and that might be the case on some cars. Anyway, it's simple to find out if that's the problem: take the hose off the manifold and suck on it. If you can maintain vacuum in the booster, everything is ok. If you can't, you need to install the seal.

a couple things come to mind-jack the car up off all four wheels, and have someone push on the brake pedal-dp all 4 wheels lock up? sometimes, with a porp. valve, when bleeding it will shut off front/rear and w/o a brake light like the fact. you wont know it
another thing that can happen, if the pushrod is to long or out of adj., it can make the brakes drag and feel hard
hopefully, the guy eng'ed. the kit properly with the right size m/c and pushrods
if you have access to a high pressure gauge you can ck it out