I put in a TA 284 cam along with a T/A manifold on my 350. My power brakes used to work fine. How ever vacuum ain't what it use to be. Installed an aftermarket vacuum canister but brakes still not as good as they were when the car was stock! Brakes are hard on start up but once the engine runs a bit things get better.
Here are some old posts of mine dyno results and real 1/4 mile results. http://v8buick.com/showthread.php?t=54585 http://v8buick.com/showthread.php?t=81540
