My 71 chevelle has power disk brakes in the front and when i try to make a burn out, my car just wont stay in place, it keeps wanting to go forward. Can this be a problem with my proportioning valve?? Can it be that i'm not getting enough pressure to the front brakes. Does it matter that there's very little clearance between the driver side header and the prop. valve located on the frame???

It could be that your front brakes need to be bled,or the rotors or calipers are worn out. My header is less than a 1/4" away from the distribution block and it has no effect at all.

Like RR said, it could be the front brakes aren't up to snuff, or it could be that the rear brakes are adjusted too tight. I don't think it's a problem with your prop valve.

chris

YOUR PROBLEM IS THAT WHEN YOU HOLD THE BRAKES ON, AND OPEN THE THROTTLE, THE VACUUM DROPS. DISC BRAKES REQUIRE HIGH PRESSURE TO WORK. DRUMS BRAKES USUALLY LOCK UP AT 600PSI. DISCS NEED OVER 1600PSI TO LOCK. WHEN YOU HOLD THE BRAKE SON, AND THE THROTTLE OPEN, THE BOOSTER LOSES IT'S VACUUM, REDUCING LINE PRESSURE TO 300-400 PSI, AND THE DISCS WON'T HOLD. CHECK OUT OUR HYDROBOOST SYSTEM. IT PUTS OUT UP TO 2000PSI WITH YOPU FOOT BURIED IN THE THROTTLE. THIS IS BECAUSE IT RUNS OFF OF THE POWER STEERING PUMP PRESSURE, AND NOT VACUUM. YOU CAN VIEW IT AT POWERBRAKESERVICES.COM CLICK ON CUSTOMER INFO FOR A PICTURE OF A BLOWN 454 CHEVELLE. THE GUY'S WIFE NOW CAN DRIVE THE CAR. THANKS, POWERBRAKEBOB

Your problem is horsepower, you don't have enough. You should upgrade then you won't need the brakes to do a burnout :D :D . Sorry, couldn't resist. Seriously though, your pads could be worn out, rotors could be worn out, air in the lines, or your tires may just grab the road well.