Ok guys i need a yes or no, will a small dual booster (7 1/2") be enough to work my power brakes? 10" vacuum, no extra vacuum needed anywhere else, 4 speed, tall valve covers, auxilary vacuum cannister to help if needed. I have heard so many opinions on this i feel like i'm spinning in circles. Ralph

ttt

so two 7 1/2"s = one 15" with 10" of vacuum? Hmmmm....


Prolly not.

10" of vacuum in whatever size container you care to specify will NEVER , NEVER be greater than 10" of vacuum.

If your brake system needs 15" of vacuum to work effeciently you can have a 55 gallon drum literally packed with 10" of vacuum strapped to the top of your car and connected to your booster(s) do you know what your brake booster(s) will see?


The answer of course is: 10" of vacuum. :)

There is no "magical" way to increase vacuum beyond what your engine normally delivers unless you use an external vacuum pump or a milder cam or in some other way make your system see a higher level of manifold vacuum.

What you CAN do is try to locate a master cylinder that has a smaller diameter bore but in all other ways fits your car. That will increase the mechanical leverage of your foot and in some small way compensate for your inadequate vacuum.