Minimum Vacuum for Power Brakes

[gzig5]

What have you guys found to be the minimum vacuum level at idle to make the E-body OEM power brakes function correctly? In this case it is a 73 Cuda. I think there have been different boosters over the years and the one in mine is pretty large diameter. I just finished the build on the engine and I'm fairly certain that I'm going to be close to the limit if not under water. I've got an inquiry in to the builder because the data on the dyno sheet was limited due to issues they were having. Engine is stock stroke 340 with a 242/247 duration cam which made 430 lb-ft at 4300rpm and 458 hp at 6300. Peaks should actually be a little higher but they had to change carb and did zero tuning. I'm guessing I'm not going to have much more than 10" but I've never run a cam like this. Trying to get a head start on looking into vacuum canisters/pumps, or hydro-boost.

 

[Chryco Psycho]

Hydro boost is awesome if you already have PS , it beats any vacuum system !
I would think you are losing assist below 12 "

 

[Mopars & Missiles]

Yeah, 10" isn't gonna cut it in this instance for power brakes.

There are other situations where 10" would get you a lot of attention.

 

[gzig5]

Yeah, I think the ultimate goal is hydro boost with a new Borgeson box. Also going to be upping the braking potential with at least 13" rotors and calipers. The budget won't allow that right away and I want to drive the car as soon as I can get it safely running. So I'm just trying to get all the potential ducks in a row. I understand hydro boost, but I don't know how reliable the vacuum canisters are, and I think I read some of the vacuum pumps can be loud. With this cam, I'm almost certain I am going to need a band-aid of some sort to make the vacuum assist work after the first couple stops.

 

[moparleo]

Hydro boost is the best.. Really best to calm down. Make the car safe before you take it on the street.
Save up some more money and do it right.
Spending money on a temporary fit must means it will take longer to save the money to do it right since you are spending money for a band-aid that means you have to save even longer until you have the funds to do a proper brake system.
Safety first.

 

[PLUM_72]

I have the Bendix 10" booster and it works fine with 14" vacuum from my mild small block. My car is a weekend cruiser and Ive never had an issue.

 

[moparleo]

He says 10 inches of vacuum. Not enough for any booster and a reserve booster just gives an extra push on the pedal.

 

[Drivun]

Had similar vacuum issues with our 72 chevelle and mounted a Black Bandit electric vacuum pump in the front fenderwell low behind the bumper. Noise isn't an issue since it's well away from the cabin and given engine/electric fan noise . Braking was way better during 5 days of driving 6 hrs/day on power tour. If pump fails claim to have 3 more stops in reserve. Longer term id go with hydraboost.