Thread: Low Power brake booster vacum

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I have a problem with my vacum presure 17 psi for my 7 inch power brake unit because of the size cam I decided to use, I purchased a auxilary vacum canister to help with the low vacum, installed it and it helps some what but the vacum gage still only shows 17 psi, and the brake pedal is only good for one application before it is hard to apply again. Has anyone come accross this, am I over looking something ? Should I have purchased a vacum pump ?
If so, do vacum pumps provide the 25 psi I need for proper operation ?

Hi Jim, is your power brake booster a single or a dual? I am sure I will be in the same boat as you since I am running a big hyd. roller cam which only puts out 10" of vacuum. So I will be running a vacuum canister hoping this will solve issue with running Wilwood disc brakes at all 4 corners. With a BBC in a 30 roadster I certainly want to be able to stop it. There is a way to run dual master cylinders that are manual (no vacuum needed) with a slave bar attachment if worse comes to worse.

Stylingz
It has a dual 7 inch power brake booster. As far as your dual masters, It would be creative to make a set up like that mounted to a fire wall on a Belair. Lets hope that there are a few guys in this forum that have the awnsers.

don't like advertising for people but
mp brakes have stand alone vacuum pumps for sale
http://www.mpbrakes.com/

Don,
Thanks for the information, It seems as if I will be looking to purchase a vacum pump, if I do not get any more feed back. maybe I can pick one up from a junk yard. Do you have any idea what newer model vehicles have vacum pumps ?

i've looked up canada way,nothing on the electrical side, couple of old ford
diesel trucks have mechanical ones, won't handle the rp's, ugly setup
keed me posted!
p.s sombody once told me a mid 80's olds used to pack a vacuum pump!?

Just an idea, Can an older gm air pump be used to create vacuuum? Never thought about it till now but it would be able to tuck in with a factory fit and available for very little coin?

Sleeve396
Good thought, Just need to figure out how to regulate the vacum pressure

Originally Posted by Jim Standley

I have a problem with my vacum presure 17 psi for my 7 inch power brake unit because of the size cam I decided to use, I purchased a auxilary vacum canister to help with the low vacum, installed it and it helps some what but the vacum gage still only shows 17 psi, and the brake pedal is only good for one application before it is hard to apply again. Has anyone come accross this, am I over looking something ? Should I have purchased a vacum pump ?
If so, do vacum pumps provide the 25 psi I need for proper operation ?

is that 17 inch pounds of vac. or 17 psi? what kind of gauge are you reading?

lt1s10
17in of vacum, not psi, sorry for the poor communication.

Thats All The Vac You Need. Thats Good Vac. WHERE HAVE YOU GOT YOUR BOOSTER HOOKED ? cant have nothing tee'd into it.

The vacum line goes from the power brake unit to the back of the carb. i will post a picture later today.

if you've got 17" of vac. at 900 rpm's you don't have a vac. problem. you may need a one way vac. valve at the booster

lt1s10,
I sent a few pictures if what I have, as you can see I have a one way valve. I tested it and it checks OK, I will check the power booster to see if it is holding the presure.

lt1s10,
I sent a few pictures for you to see, I checked the oneway valve and it checked OK. I will check the power brake unit to see if it is holding pressure.