Timmer if your master cylinder was designed for drum brakes it allready has residual pressure valves built into it so no need for extra valves. Adjust your brakes up hard so you cannot turn them this centers the shoes then back them off to a slight drag, but not more than seven notches. If all parts are kept adjusted your master cylinder will probably be okay, the only time you would definatly have a problem is when you let things get out of adjustment, more travel more fluid needed
