My set up:
87 firebird with power brakes
383 LT1 with a much larger cam this year
stock front disks
9" rear with explorer disks

Last year my brakes were not the best but the got me stopped at the end of the track. Over the winter to help the brakes out and get more RPM (foot brake) off the line I added a willwood rear proportioning valve and a vacuum reservoir tank.

I gutted the internal valving on the rear side of the stock combination (proportioning) valve to get 100% pressure to the rear and added the adjustable willwood in the rear line. Then I installed the vacuum reservoir up near the nose of the car with a 1/2" hose from the engine and a 3/8 hose to the stock brake booster. Then me and my buddy bench bleed the master twice and the rears about 100 times.

Any ideas why my brakes barely stop the car?

 

The car has a solid pedal when it is off but once moving it feels a little soft and even when pushed to the floor it barely stops the car?

 

You should have bled the fronts also.

If you had to bleed it 100 times instead of 1 time means you had no confidence in your procedure.

Due to the fact you can push it to the floor you most likely have air in the line(s).

It might save you $$$$$$$$$ in the long run to go to a class for brakes.

◙◙◙◙◙◙◙◙◙◙◙◙◙◙◙
Happy Racing!

 

Ya I hate brakes and we did not bleed them 100 times I just meant more then enough. I did not blead the fronts and that is where I will start but I never opened up the fronts.

I am curious what do powere brakes feel like with a bad booster and is there a way to check one?

 

A bad booster will give you a hard pedal and very weak brakes.

Because your pedal goes to the floor, that’s the problem that needs to be fixed before you can judge the booster.

◙◙◙◙◙◙◙◙◙◙◙◙◙◙◙
Happy Racing!

 

check your master cylinder... a foot to the floor in my own experience needed a new master cylinder...