I may have misworded some..........I was referring to "the old days" ----- a car with a factory diaphragm such as Chev would tend to "stick down" because of the design of the clutch. On some you could actually depress the pedal in neutral, rev the engine, and feel the pressure become less
If you swap one into a Mopar the pedal pressure for a diaphragm is normally less than a BB so you don't NEED an over center spring, plus you are RIGHT...........an OC spring WILL tend to "help" a diaphragm stick down.
