vacuum 9 inches
Get yourself a SSBC electric vacuum pump and have a steady 18--21 inches of vacuum. You only hear the pump when you hit the brake before you start the car. Turn up the sterio and block it out....LMAO.
My 35 coupe with 7" dual diaphram booster 1 1/8 bore master , 4 piston wilwood brakes all around, stopped like crap and was a heart stopper when driving until i got it sorted with the vacuum pump. I highly recommend it.
I had 13" max at idle and 2000 rpm, it just doesn't work when your running a healthy camshaft with lift and duration. Pump solved the problem.
I already bought another for my new 35 steel chev roadster build.