power brake vaccuum problem ??

[iluv69s]

This is not a Supercar, but thought I would ask. Hope noone minds. Have had this 57 Chevy in the family for years that i am forever tinkering with. A few years ago, I retrofitted it with later drivetrain, suspension,etc. Since then, she loses the power assist on the brakes at low idle. Not very safe for a car that weighs so much. It has aftermarket power disc setup. It is apparently a lack of vaccum problem. I put a ZZ4 383 in it and the 425 hp cam kit that GM sold at the time and it has the Barry grant six pack setup also. I did not think that cam was so radical to cause vaccum problems w/ the brakes...anyone have experience w that motor/setup? I'll probably try another power brake booster first, but,is there some vaccum assist available to add so I dont lose vaccum? Thanks SYC... feel free to move this if it is in the wrong place..