Proportion valve

388dart said
master cylinders are also not the same from drum to disc...an all drum cylinder would have residual pressure valving on both ports

Pleas expalin further if you could - and what might be the side affects if you retained the drum master cylinder when converting fronts to disk?

Drum brakes have a residual valve so there is always about 2 - 5psi in the lines to keep the wheel cylinder pistons up against the brake shoes. There are some disc brakes that need residual pressure to keep the piston up against the pads (Corvette 4 piston brakes require this residual pressure) but most disc brakes do not need this residual pressure. Single piston/floating calipers do not and if you have a residual valve in the line the disc brakes will drag because of this pressure.

Now I have a question for the Kelsey Hayes guys. I just purchased a parts car with this setup and I am going to put them on my Duster. I have everything so I am just going to swap everything. Just so I know do the Kelsey Hayes calipers require a residual valve like the Corvettes being they are also 4 piston calipers? Or did Kelsey Hayes have a way for the pistons to stay out against the pads and Delco Moraine did not on the Corvette?

Chuck