WHO'S GOT THE SCOOP ON RESIDUAL VALVES?

I can tell you this: my car came with 4 wheel drum brakes, which are still on the car. I removed the single m/c & replaced it with a late model [ early 2000 model ] dual m/c. This m/c was used with 4 wheel disc cars & did NOT have RLPVs. I also have the auto brake adjusters working. My pedal moves about a 1", maybe 1.5", & I have a rock hard pedal.