[Jack21]

Tom,

If you look at the brake component location on some '30's and '40's era cars, the master cylinder was located by the floorboard, and below the height of the wheel cylinders. Brake fluid could siphon back into the master cylinder under those conditions. The residual pressure valve functioned as an anti-drainback valve. If your master cylinder is located above the height of the wheel cylinders, you shouldn't need residual pressure valves. Something else is causing your wheel cylinders to retract. Look at your parking brake adjustment.