Enough vaccum for brake booster

[Mike71Cuda]

I just talked with the guys at Master Power brakes about my booster/mstr cyl issue and the tech brought up a great question, enough vacuum? He said I need 18 inches at idle/neutral to not have issue at cruising speeds. If not I need a vacuum pump. I am going to check tonight, but what has been your experiences out there? My hemi is a stock build

[matt63]

I've got 12" of vacuum at idle and it works fine, perhaps a little soft. 

[loco340cuda]

I've got 12" of vacuum at idle as well with power brakes.  It seems to work reasonably well, but in stop and go traffic I have to be careful to not follow to closely due to the pedal gets soft and the car doesn't stop real great.  I'm going to convert the car to manual brakes in the not too distant future.

[Mike71Cuda]

I have been told that with the Hemi I will need the help of the booster. Thanks for the info

[73EStroker]

Take a look at about the last or second to last Mopar Action magazine issue. In there is a restomod Cuda with the correct brake unit for a highly modified muscle car. That is a Hyro-boost unit driven off a PS pump.
My friend has a 64 Corvette that had all kinds of problems with brakes using a vacuum system and he has an 81 Corvette system on it. He put a hydroboost on and now that car stops similar to modern Corvettes or Vipers. Others might say use the standard non-power master cylinder but that is ludicrous to attempt to stop in an emergency with those poor antiquated braking systems. I picked up a good working hydro-boost unit off a Chev Astro van last week for $26. It has been checked and ready to go. Cars that have incredible acceleration and lousy brakes are not a good combination - I drove my friends 69 340 Cuda with manual brakes and at 100MPH I was wasting my time pushing the pedal.

[Mike71Cuda]

Stroker
Thanks for the info where did you get the boost unit from the Astro van? New? Used?

When I had the 440 and we had a track day at Englishtown, the first few runs were fun until I started looking for the brakes going thru the traps at 100+ and the safety fence started coming up quicker and quicker!

[Chryco Psycho]

any drum brake system will overheat quickly , disc are fr better for resisting fade , this is a must have upgrade , for serious driving rear discs are needed for the same reason , in typical driving the drums will cool enough between use , but for autocross type driving or similar where brakes are used both hard & often rear discs are a good idea
 Not alll Astro/ Safari vans have hydro boost systems , later 4 wd versions seen to use them & a lot of truck applications have them as well , I would start looking at the local wreckers for a good unit , the only down side to this is you need to have power steering to make them work

[67Vette427]

Which Hemi and what cam? Is it the crate 426 or 472 or bigger? I ran the 472 crate in my Challenger and the cam in that motor reduced the vacuum down to about 8 inches at idle and the power brakes didn't have enough vacuum. To solve the problem I ran an electric vac pump. I run manual brakes on both my Vette and my Cuda since both have radical cams. There are systems out there you can buy that are non-power...The Vette is four wheel disc and it stops real well without a booster.

[Chryco Psycho]

I found another Hydro boost on an Astro in the wreckers 2 days ago