So I switched the old treadle vac out of my 60 continental in favor of a dual 7" booster and a .75 bore dual master. The treadle vac bore was around .65 or so, but the old treadle vac had less power assist ~6" single diaphram. The pedal is somewhat stiff for the first 1" or so of travel until the brakes engage, but once they do, the brakes are very responsive. The car has a great big vacuum resivour that isn't connected now. Stock 430 motor 18-20" vacuum at the manifold. Vacuum assist line is hooked up to manifold. Any ideas why the first 1" of travel is soo stiff?