Loosing pedal at low speeds

[JLM]

On my 69 Firebird I have a set of MP Brakes front disks with a their powerbooster and new master cylinder.

While driving the car the brakes are great when you are at speed. however as speeds get to about 20mph and below the pedal becomes very hard and unresponsive. You've really got to mash on it to get the car to stop.

The engine has a healthy cam in it but nothing that I would consider to be "wild." Could lack of vacuum be my issue here? I haev the vacuum line to the brake booster run from the back of the carb rather than the intake manifold.

Any thoughts on this would be helpfull. Thanks guys.

[Travis B]

Do you have vacuum canister of any kind?
With the car in nuetral with your foot on the brake rev the engine you should feel the pedal move if it is a vacuum problem???
When you say not to wild.....what are the specs?

[JLM]

I'm not sure on the specs. This engine was put into the car about a month before I purchased it. The originall owner was turning the car into a street.strip car but fell on hard times.

The cam is healthy enough to need added compression and a larger stall. I wouldn't say it lopes like crazy but the idle is not smooth by any stretch of the imagination.
I do not have a vacuum canister or pump.

[Travis B]

It sounds like a vacuum problem to me! I would try a canister??

[JLM]

Would a canister be the best choice for possible road course events? I could definitely see it being effective in normal driving conditions but at track events it may not be the ebst choice? Any thoughts on this?

[Travis B]

You might want to go with an alternative setup....Hydroboost,manual,etc
I am not sure JLM maybe someone will give us another opinion??

[6'9"Witha69]

IMO canisters are not a good choice for track events. I have buddys w/ canisters and any more than 3 quick accelerate then brake attempts and the canister is out. Canisters need some time to fill up and the constant accelerations don't allow this time. Hydroboost or Manual is my recommendation and I lean heavily towards manual (I don't like the idea of my steering pressure system and brake pressure system being linked, just my .02). Besides, it loks a lot cleaner.

[JLM]

I may have to look into the hydraboost system. I could always run an electric vacuum pump as well. I think that would be the cheapest solution aside from running a canister.