Technical Hard pedal, touchy brakes

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?

 

wild guess is the master cylinder bore is way too small for a good booster with drum brakes.

 

The new MC is actually larger than stock, which would explain a stiffer pedal when the brakes engage, but I'm puzzled why it is stiffer before engagement?

 

I'm inclined to go along with Jim on this. That small bore is going to put a lot more pressure than a 1 inch bore master cylinder would.
As for the binding or tightness in the first inch, is it possible that the geometry of the pedal, pushrod and booster/master cylinder are off a bit? If the pushrod isn't being pushed in perfectly straight it may be pushing the piece it pushes against off to one side just a fraction causing more friction until you get past that point.

 

Hmmm...I'll measure the pushrod angle

 

Try this link for an answer: http://www.mpbrakes.com/troubleshooting-guide