Cant hold boost vacume brakes

[TWISTER]

Im getting ready to go racing and changed over to vacume brakes last year, I have the s 10 cylinders long shoes and didnt have a problem with before w the Power master at 10 psi on the line but now I can hold 2 or 3 then I start to spin the MT drags. Sometimes it will hold 10 and sometimes not. I adjusted them up tonite and still no luck. I also have the TTA vacume blosk and white check valve that eas working last time I checked. I rev it up and mash the brake on the rev down and stilll have no luck. Any suggestions on this and why it seems to be intermitent? Thanks for any help. Marty

 

[POWERBRAKEBOB]

Hydroboost Vs Vacuum Vs Powermaster

When You Bring The Car Into Boost On The Line, The Vacuum Booster Can Only Rely On Any Vacuum Left Inside The Booster That The Check Valve Can Hold. With The Hydroboost, The Pump Spins Faster As The Rpm's Come Up. It Just Locks The Hydrobost Down Harder. Guys Report On This Forum, That They Can Hold Up To 22lbs Of Manifold Boost With Their Foot On The Brake. The Cars Just Leaps Off The Line. 22lbs Of Boost More Than Doubles The Horsepower At Launch.

 

[TWISTER]

I know this topic has been beat to death and if Im gonna change to a different brake setup I may as well get a T brake. I just dont know why it will hold one time and not the next. I plan on re checking the valve and bleeding again but after that Im outta ideas. Thanks for your help but I like the vacume brakes......Till its time for racing that is..

 

[TWISTER]

Well I changed the check valve, cleaned up the shoes that were glazed a bit and bled all the brakes and I still cant hold boost........Why dont I here alot about people putting Transbrakes in where they cant get the vacumes to hold? Thats my next step I guess cause the Pmaster isnt going back on. Any ideas on which way to go here? Thanks.

 

[POWERBRAKEBOB]

Hydroboost Vs Vacuum Vs Powermaster

Trans Brakes Are Great For Drag Racing, But Still Won't Stop The Car In Traffic. Most G.n.'s Are Street Driven, And Mostly For Fun. Also The Trans Brake Does Nothing For Road Racing Or Spirited Street Driving.

 

[TurboBuRick]

Try leaning idle out. One thing I noticed about vacuum breaks too much gas down low will douche down the vacuum. The break booster gets its max charge at idle when the throttle plate is closed. Get it more vac and you will hold.

 

[TWISTER]

The brakes feel better than they ever did on the street I just cant seem to hold boost on the line. I will try to lean it out on the bottom some more and see if that helps. Thanks.

 

[vader87]

Brake bypass valve! Bypasses the proportion valve giving you twice the rear brake holding power.

Here is a thread:
http://www.turbobuick.com/forums/general-turbo-buick-tech/212001-how-much-boost-line.html

Scroll down to my post because the first few are about line locks.