I've got my 71 chevelle running good and I have put disc brakes on the front. I have the right prop. valve and Mastercylinder. I bench bled the m/c when it was almost level and i am pretty sure I got all the air out. I think I will need a new booster but when I drive it I can slam on the brakes and the wheels wont lock up on a dirt road and it takes twice as far as it should to stop. Everything is new on the front and rear brakes and I have bled them many times. Can you guys tell me what the problem is. Thanks.

Your booster may not be providing enough vacuum boost or you have a leak. I had to change to a dual diaphragm booster on my 64. Large duration cam will give you some boost problems.

I know my booster is probably bad but the car should still stop without vacuum. I disconnected the vacuum on my daily driver and it still stops hard you just have to push harder on the pedal. This is beginning to bum me out.

I had the same problem when I added power brakes and it wouldn't even do a skid stop because my cam was a little big. I then found out my pads in the front were glazed. So I put on new pads and my teacher then told me to do a couple of hard stops to brake them in. Can you stop better at higher speeds, not to high, like 35mph? I would say do a brake inspection all around. Try scratching out a good chunk w/ your screw driver out of each pad. That might be your problem too: service brakes. If that doesn't work, try a vacuum canister.

It could be the wrong master cylinder.

The parts book my guy ordered from had the numbers for a 70 and 71 master cylinder reversed. The 70 has a shorter pin and if you have a 71 cylinder on it, it will take about 1 1/2 inches of pedal travel before the brakes ever begin applying.

The car feels like it has great breaks until I start to drive it. It just doesn't stop like it should at any speed. Everything up front and in the rear is new, such as drums rotors pads shoes calipers. Once I start to drive it I can put all my weight on it and it gently slows down.

Try calling the place you bought it from and tell them everything to there tech line.

This might sound easy, but check to make sure that the pads arn't in the wrong spots. You want the shorter pad in front if I remember right. This might also be a problem.

Have you tried re-adjusting the rear brakes? Just a thought.

This may sound like a stupid question, did ur car have power brakes before? If u didn't have them did u put the brake pedal push rod in the lower hole of the pedal?