how much vacuum for power brakes

[dinnut]

if im going to run an original power booster setup on my truck how much vacuum do you need?

[Cat Fuzz]

Manifold vacuum should be sufficiant.

[FRENCHBLUE72]

Should be a port off the back of the carb(depending on what carb you have) that you can hook up the vaccum to..

[dinnut]

thats not what i asked. thanks tho. i have that port already its blocked off with a spark plug.... later on i will be going to aftermarket intake and carb and probably cam and one cam i saw advertised 10-12 inches of vacuum at idle and wondered if this is enough to run a power brake setup

[FRENCHBLUE72]

I got 30 inch's of vaccum on my 350 powered yota.. Brake's work killer..

[dinnut]

is 30 a lot or a little? i dont know how much is a lot and how much is a little

[rage'nrat638]

would need aleast18- 20" of vacuum to run power brakes with any good pedal response....
30" of vacuum is kick buttt......

why what's you got?

[cableguy0]

im running power brakes with about 8" of vaccum but without a vaccum canister that isnt possible and if you ride the brakes you will lose them

[dinnut]

oh. havent thought about the vacuum canister thing. i want a good fast engine but i also need power brakes... the cam im looking at puts out about 10-12" of vacuum. i dont know bout my truck its stock except for hei and headers/duals and chrome air cleaner

[Leinie]

Last time I checked, my blazer was running 16" vac and the brakes work just fine. My cam, intake and carb are not stock, so it runs a bit under stock specs.

[cableguy0]

with 10" of vaccum u can run power brakes you will just have to buy a canister. no biggie unless you use the brake pedal for a foot rest then you wont be able to stop when you need to

[lukecp]

I pull a little over 19" of vaccum with my truck (204/214 cam) and the power brakes work just fine.....no worse than when i had a completely stock engine.

Remember to stay fairly mild on the cam specs....what cam are you looking at? It will take a farily large cam to drop your vaccum into the 10-12" range at idle.....you don't want to stick a huge cam in a engine with stock heads and like 8:1 compression....even if you have a good induction and exhaust system.....it won't run very good and you will have crappy mileage and driveability.

[dinnut]

i was looking at an edelbrock performer rpm cam i think
http://edelbrock.com/automotive/cams_index.html
but i wanna go with a comp cams cam. something not too radical but gives me good burnout power.
i bought the comp cams master catalog and its frickin huge and has a cam for everything

[lukecp]

You don't want tha Performer RPM cam in a stock motor.....it won't run very good. It is basically an old 292 cam....lift is over .500". It would proalby pull the pressed in studs out of a pair of stock heads in a hurry. To have a cam like and have the motor run good, you would proably need a set of heads that flow well at .500" lift, compression in the 9.5:1 or higher range, a high stall tourqe converter, and rear gears around 3.73 or lower. For a stock engine, converter, and high rear end gears, you would be much better off with something like a Crane 266, Comp 268H, Comp XE262, or something along those lines, with around .450" total lift and duration around 210 degrees at .050" lift. Then you would have a smooth idle, good low end power, good gas mileage, and more power overall than with a stock cam.
You should have plenty of burnout power with the smaller cam

[dinnut]

Thanks. what are you running? i like the old school lopey sound and thats kinda what i want in my truck but i guess a smooth idle would be ok....

[lukecp]

Right now i am running a cam that is too small for my motor, a Wolverine Blue Racer grind with 204/214 degrees of duration @ .050" lift and lift of .420/.442. Basically the same thing as a Summit 1102 cam. It did work good in my motor when it had 8.5:1 compression and 1.72/1.50 heads, but now that i have a better flowing set of heads on it and higher compression, it dosen't work that great. Stops pulling at a little over 4k rpm's. If i keep my 3.07 gears, i will upgrade to a Comp XE262. If i get 3.73's and the truck isn't my daily driver anymore, i will proably get a Comp XS268 mechanical solid lifter cam.

The 268H should have a nice lope at idle....every 350 i have heard with one sounded pretty good. Could defenitly tell there was a cam in there. The Crane 266 would proably be pretty a little smooter. I haven't heard an XE262 yet, but everyone says it will sound pretty healthy at idle, with a lope.

[miket]

For reference purposes the ZZ502 cam allows for roughly 12"...my brakes are "okay"...but not do to lack of vac....they need to be bled.