Power Brakes and Engine Vacuum?

What is the minimum vacuum (at idle), required for power brakes to work properly? Thanks

I've found they work fine with 12". I wouldn't want to have much less.

And if you're worried you can always add a vacuum reserve canister to help with the duties...

I ran a car with 6.5 inches but I really wouldn't recommend it. Without a cannister I would think you would be just fine with 10"

I need to put good working engine in my Challenger for a while while I decide what to do with the original small block. All I have is big blocks. The smallest cam is a street hemi grind MP.474 280 which makes anywhere from 9 to 12 inches of vacuum depending on idle, neutral, in gear, engine temp etc. It idles nice in gear at 700 rpm or so. I think I have most of what I need to make the swap without grief. My other engine choices would be more fun, but likely unsafe when it comes to stopping. I kind of thought this might be the lowest vacuum required to retain safe and effective power brakes.

I have 8" of vacuum at idle, in gear, with my 440. The power brakes work fine. I do have the engine in a truck with the dual diaphgram brake booster.

My 68 charger has 10.5" at idle and the power brakes work fine.