no[little] power brakes assist

thanks for the information, when I spoke to the company I bought the front power disc. brake kit from told me I need a min. of 16 hg, 18 would be best. I will check out what you say , also I will install a fitting into the intake manifold to draw vacuum direct I now have a 't' in the line at base of carb,so I can hook up the power brake booster and my pvc valve