How much vacume shout I have for my power breaks to work properly

[troy.70R/T]

How much vacuum is need in order to operate my power brakes properly. Is the port on the intake the best place to get the most vacuum?

[b5blue]

I think my old 509 cam build ran about 8" and with an added reserve canister they worked pretty good. At 14" with my resto cam they worked super until today! (something has gone wrong, I got brake but no boost!)

[maxwellwedge]

The port on the intake is the proper/best spot.

[histoy]

I ran the 484 Mopar purple cam in my '68 GTX with a 4 speed.  It carried 11 inches of vacuum and the power brakes worked fine.  Currently my '68 Coronet R/T with an auto transmission has 11 - 12 inches, and the power brakes aren't quite as good as I'd like.   Running less than 11 inches of vacuum would probably be iffy in my opinion.

[Musicman]

18" is the standard minimum for best operation, but they will work with less obviously, just harder.

[troy.70R/T]

Thanks for the help guys.   

[greenpigs]

I think my old 509 cam build ran about 8" and with an added reserve canister they worked pretty good. At 14" with my resto cam they worked super until today! (something has gone wrong, I got brake but no boost!)

Sounds like you need a new booster or seal.

[bobs66440]

18" is the standard minimum for best operation, but they will work with less obviously, just harder.