I have been searching but not yet found any solution to my problem. All new everything, brake system. Reproduction parts. Front disc conversion. I bleed the brakes with the help of my wife, all went well and all air seem to be removed. Afterwards my brake pedal is very hard to push. It will stop the car but something is bad wrong. I talked to Mark Remmel today he says my cam should supply enough vacuum, i thought i had 15 inch of vacuum but today my gauge says only 12 inch vacuum. The motor runs great or seems to, but ill have to admit im not good with a timing light, i did my best and it really seems to run very well. It fires right up and has alot of power, but perhaps there are carb and timing adjustments i could make to create more vacuum? Im almost done with the build, i drove it out of the garage into the sun for the first time in 4.5 years, im excited.
Any ideas on my brakes would be appreciated. If the porportioning valve got out of center what would the effect be of that? And how do you center one?
Thanks
Steve

 

A very hard brake pedal is usually a bad power booster.

 

Thanks Eric, I appreciate your reply

 

X2 on the power booster. I ordered a brand new one from Motorcity (Inline Tube) and didn't install it until 3 months later. It was bad out of the box, same symptoms as yours. They would not take it back after much communication. I finally gave up, told them they won and painted my old one and re-installed it. Looks and works great. I sure was glad I put a larger nut under the stock nut on the lower inner stud to tale up some of the long thread. Much easier to switch it out which ended up sooner than I thought or would have liked. I have a great looking Inline Tube power booster for sale if anyone wants.

 

I ran into this very same issue with my friends 66 Chevelle. It had been to 3 shops, no one could figure it out. I took it off and replaced it with his original also. Long story short, I had to put an aluminum rod down into the M/C actuator hole because of the mismatch between the old booster actuator and the way new M/C from the kit he bought mates.

 

Thx Eric, I believe you diagnosed my issue as well.

Randy

 

Are you saying the actuator rod from the booster wasn't long enough to push the master cylinder sufficient to fully apply the brakes? I didn't follow the aluminum rod being put into the master cylinder actuator hole.

 

The booster had rod style actuator where as the diameter went straight into a hole bored into the M/C actuator and would not engage. You'll know if you run across the issue, the booster need something to push against to apply the brakes. I cut an aluminum dowel, close in diameter, to the proper length to allow a small amount of pedal free travel and slipped it into the hole

 

Again thanks guys, but do you think 12 inches of vacuum is enough?

 

On my car the brakes didn't work at 100% with around 14-15" bouncy vacuum. After re-tuning the HEI so the initial advance was around 20º the vacuum came up to a steady 16" and the brakes worked fine. So from this experience I would say 12" is too low.

 

12/13" is not uncommon with a performance cam to operate power brakes. You can install reservoir to help maintain levels if required. Your vacuum in itself will not cause a rock hard pedal.