Drag car brake/proportioning question

73smallblock said

I ran for several years without a prop valve. I factory disc's up front and wilwoods's in the rear. U always had a bad shimmy from the front under hard braking running 1/4 mile. Someone said that I may have to much braking in the front and it's on the verge of locking them up. Dr. Diff said this may may be a problem and would have to put a adjustable one on the front brakes only, which I already plumed in for this year.

From what the Dodge manual said about my old truck is that the factory prop valve sends fluid to the rear first. Once it reaches xx internal pressure it then sends it to the front. I would imagine that's how they all work.

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No, that’s not how they all work. All the factory stuff for these cars is intended for use with a disk/drum set up. How it’s balanced and proportioned was intended to keep the disks and drums, which take different amounts of time to apply, working in unison.

If you’ve gone to aftermarket brakes, 4 wheel disks etc then adding an adjustable valve is the only way you’re going to get the front and rear balance set properly for your car. Maybe running with the factory distribution block or prop valve will get you close enough for most braking situations, or maybe you’ll get lucky and it’ll be right. But that’s unlikely, especially when you start mixing and matching aftermarket set ups.