Im currently working on a 75 firebird with power brakes, I have changed both front calipers, and both brake hoses, master cylinder and proportioning valve. I cannot get a good pedal at all. The back brakes will lock up before the fronts and the pedal is low. The system is properly bled and there are no leaks. Does anyone know if there is a vacuum canister in this car? 350 4bbl carb. Cause im starting to think its a vaccum issue, other than that Im loosing hope. Anyone have any ideas?

PS Master Cylinder has been properly bench bled.

Any help greatly appreciated.

check vaccum at idle, what do you have?

check the check valve on the booster, make sure it holds vacuum

Ill check the vacuum and valve tomorrow and let ya know. Thanks!

Got busy with work this week, going to check the vacuum now, what should it be at?

I think its supposed to be around 15 or better. If its less, you may need a vacuum pump and reserve.

as for the check valve, just make sure it hold vacuum. Attach a hand held, or power, vacuum pump and gauge to the valve with it attached to the booster and pump it up. Let it sit and see if it holds