a prop valve for Disc brakes sends less brake pressure to the rear, since drum brakes require more pressure to work. So i have read. i did a brake swap, eg5 stock brakes to DC2 brakes front and rear, the DC2 had ABS so i re used my old prop valve, worked fine for me, the car felt less squirelly under brakes. i did use the bigger brake booster and MC. ABS cars have slightly different line fittings for the MC to Prop valve it wasnt a straight swap in for me