Voila.
Walla makes no sense. :D
4 wheel drum systems rely on wheel cylinder sizing to determine proportioning. Front disc, rear drum systems need a proportioning valve to reduce pressure to the rear to reduce the risk of lock up.
4 wheel drum cars still often have a "distribution block" where the master cylinder lines attach.
I've read in Mopar Action several times where Rick Ehrenberg berates people writing in asking about brakes. They incorrectly refer to the distribution block as a prop valve and instead of explaining the difference, he just states that the 4 wheel drum cars don't have proportioning valves. They may go away pissed or confused because the block that has 5 lines going to it HAS to be called something. He is smart but does come across as a prick sometimes.
Some GM cars had brake pedals that had 2 holes in them for the push rod that presses into the master cylinder. Top hole for manual brakes, bottom hole for power. The higher/closer the hole is to the point at which it pivots, the higher the pedal ratio. With the Mopars, there is some type of bellcrank linkage to reduce the pedal ratio. Power brakes have LESS leverage designed into them since the booster aids in the stopping action.
You can gain better pedal leverage by drilling a hole above the stock location. I did this in my '70 Charger and it made a noticeable difference.
