[Seattle Sam]

Hi Tom,
I definitely would not disable the rear brakes by adjusting the proportioning valve. A line lock (roll control) is the way to go with a stick car to help with burnouts and staging.

Before adjusting the proportioning valve, I would first make sure all your individual brakes are adjusted properly. Lift each wheel off the ground to check. Your front disks should offer a little drag as you spin each wheel, and you can adjust the rears until you feel drag then back them off a little (If you have limited slip you need to get both rear wheels up at the same time).

If you have a standard brake set-up (factory size brakes front and rear) you might want to use the standard factory proportioning valve that will not require any adjustment. If you have beefed up your brakes and need an adjustable valve, call the manufacturer and ask them what setting they recommend to start with.

Then I would find a safe, open, low traffic area for testing (maybe a big parking lot after hours?). Speed up to around 20 MPH and stop real hard, to the point of lockup. If the fronts or rears are locking up first, then make an adjustment to the proportioning valve. If one wheel locks up, check out the brake adjustment on that wheel instead. If they seem to lock up all at once, then you are done.