How Much Boost with Vacuum Brakes ? ?

[turbo1962]

I have the conversion vacuum brakes, i up graded the rear S10s new brakes all the way around . i can only hold 2-3 psi of boost with brake . will i need a vacuum pump to hold 10 psi boost to make the launch.:biggrin:

 

[jurassic five 7]

No need for a vacuum pump!

Made sure there was no air in the lines? As in you bled the brakes right?

Use the E-brake!

-Adam

 

[turbo1962]

The brakes work great on street. have know air in the lines . Maybe burn out has worn the new brakes.

 

[jurassic five 7]

Like i said....

E BRAKE!!!!

 

[BlackMetal]

A lot of guys complain about not being able to build boost with vacuum brakes, seems like a common down-side.

 

[Rodney87GN]

I did S10 wheel cylinders and 4 long brake shoes, bled them real good, and I'm able to hold 10-12 psi.

Or just get a transbrake.:biggrin:

 

[turbo1962]

Going to go back threw everything,see if i missed something.
Thanks for the help.

 

[turbofish38]

It aint the booster if you cant hold at least 10 pounds. First off you have to have the technique down before you can say the brakes wont hold. Idle up to the line, mash down on the brake pedal and than give it throttle. You can have all the gimmicks in the world but you wont do chit with out some tires and traction. Strap on some slicks. Street tires wont hold. If you cant hold boost with the slicks than something isn't up to par with the rear brakes. Sometimes the problem is in the trans and engine too. Do you have your tune spot on?

 

[POWERBRAKEBOB]

Hydroboost Conversion

The Hydroboost Brake Booster Runs Off Of Power Steering Pump Pressure. No Vacuum Involved. Guys On This Forum Have Reported Building 22lbs Of Boost With Their Foot On The Brake. As The Revs Come Up, So Does The Pump Speed. It Just Holds The Brakes On Harder. These Units Can Deliver Up To 2000psi To The Calipers. When The Brake Is Released, The Pump Is No Longer Under Load, And Does Not Affect Horsepower. Building Manifold Pressure Against A Vacuum Booster Will Cause It To Let Go. Vacuum Boosters Need Vacuum To Work, And Supercharging Is The Opposite Of Vacuum. A Drag Race Start On A Gn Requires The Rpm's Come Up To Spool The Turbo. Most Cars Will Red Light At 1-3 Lbs Of Boost With The P/m Or The Standard Regal Booster.

 

[turbo1962]

I have ET streets 1050x26 I haven't thought about using the E brake to hold boost. might be a trick to pulling the handle at the light. my tires start spinning about 2# maybe the tires just are not holding, do not see anything else over night vacuum still on brakes know bleed of.

 

[turbofish38]

I haven't thought about using the E brake to hold boost. might be a trick to pulling the handle at the light.

Think about that statement for a minute. Fix the problem first instead of trying to band aid it. The park brake is just a mechanical lever. Your brakes work on hydraulics. If you cant hold boost or they dont lock up in a panic situation than you have bigger problems. Heck,even my NA 455 Regal stalls out when powerbraking the crap out of it. Aint no difference in what type of booster you have. I have 11 inch drums on the back of my GN with vacuum booster and I can hold the brakes way past 23 pounds if I care too. According to everybodies logic here I shouldn't be able to do that with a vacuum booster.

 

[BlackMetal]

I have 11 inch drums on the back of my GN with vacuum booster and I can hold the brakes way past 23 pounds if I care too.

How loose is your converter... maybe some of these guys have more trouble holding boost because their car is ready to pull through the lights at 2grand.

 

[BlackBandit]

Also, if you're trying to hold boost after a burnout and you don't have a linelock you're wasting your time. The heat that's developed in the rear brakes while doing a burnout using the foot break is tremendous and renders the rear brakes almost completely ineffective.

 

[turbofish38]

Stock D5 convertor. If you cant spool than your problem is in your tune.

 

[Steve]

I think the brakes get the blame for this often when its actually a different problem. My car has a PM and stock replacement brake shoes and it will hold 10 psi no problem at all. It will likely hold more but it will just blow the tires away as soon as I nail it at 10 psi so more isn't going to do me any good. My first GN was 100% stock with PM and original brake shoes and it would hold 6-7psi. I think there is another problem.