‘66 Barracuda Brakes Suck — Proportioning Valve Maybe?

Disk brakes always require more pedal effort than dua-servo drums.
Drum brakes of this design are self-assisting.

Disk advantage is mostly in repeated high speed stops and long downhill situations.

ps. Nothing on that prop valve's exterior looks anything more than surface patina. The body was always a -as cast- exterior.