vaccum question ( brakes )

[krazykyle]

does anyone know what pressure of vaccum you should be producing at idle for the brake booster.it's seem that i might have a large cam that isn't making much vaccum and my brakes still seem soft.

 

[JBreu]

What size cam do you have....I'm running the edelbrock performer rpm with 488/510 lift...no issues at all with mine???
Just curious is all...

 

[krazykyle]

well i found some paper work on the motor because i bought the motor used 335/503 .my pedal gets real soft at idle and stiffens up when i give it some gas.

 

[JBreu]

Not sure how much vaccume is needed for the brakes.....but you shouldn't have that problem as your cam isn't that big...is there a check valve in the vaccume line ? If so maybe it's bad......Are you running the line from the carb or the intake? If from the carb , you might want to switch to the intake. BTW, I'm not sure which is more beautful...your car or your gal 🙂

 

[pontiacgp]

if you loose vacuum to the brakes the pedal don't become soft...the pedal goes hard.

 

[crash]

if you loose vacuum to the brakes the pedal don't become soft...the pedal goes hard.

Agree.

If you have any sort of a soft, or mushy feeling brake pedal then you need to bleed the brakes. In some cases the fluid might be contaminated and need changed out as well. Brake fluid is supposed to be changed just like engine oil and trans fluid, though I can't remember the interval off the top of my head, but I know that most people ignore it.

 

[krazykyle]

i'm running the vacuum off the back side of the manifold.i bled the brakes several times but just the back ones becuase of the rear end swap.do you think i have to bleed the fronts also.

 

[krazykyle]

ok i bled all four brakes and the problem i seem to be having is that the brakes are hard but everytime i give it gas it slowly go to the floor.give it gas goes down gas down.what is the problem? :?:

 

[Bonnewagon]

When I used the Crane 278 cam I needed a vacuum can. I think the vacuum was around 17 or 18 inches. I was surprised to need the can but it solved everything. Why not run a vacuum line over to a known good car with 20" or better vacuum as a test? Those vacuum cans have gotten pretty expensive lately, so test first.

 

[krazykyle]

well i'm drawing about 15 pounds of vacuum pressure at 1100 rpm and the brake booster is holding pressure.anyone have a clue why my brakes still seem soft.rear brake new adjusted rear wheel cylinder new,front brake are good and bleed.