KP wrote:
"I thought the booster had to physically/mechanically interact with the master cylinder."
It does - but it is physically/hydraulicaly interacting - in my set up, the front half of the MC supplies pressure to a 'control cylinder' that valves the supply of vacuum/ambient air pressure to the front end of the vacuum pot thru the line seen on the 'flip side' photo in my post above. this moves the pneumatic piston rod into the hi-pressure bore where it shuts off the lower pressure side and pushes the plunger at a 2:1 ratio for the power part of power brakes. This, in turn, acts on the small end of the control bore (also at 2:1) to modulate brake pressure by pushing back the control piston regulating the supply of vacuum/ambient air pressure to the vacuum pot, a typical analog control loop.
There was a photo of a 69 duetto alfa somewhere here that uses the very same concept only it has ATE components and had two of these 'remote' boosters valved for the right front/rear brake balance, much like the 007-ish AMs, IIRC there were some cars (lambos?) that varied the balance by sensing suspension position (nosedive) to regulate the two boosters!
These units are beginning to remind me of the way SU carbs used to be viewed, impossible to keep in tune! Heh, if you can't keep SUs in tune, best to leave Webbers alone! The more I research the Girling servos the better I think they are, just a little "hidebound" in their choice of seals.
Cheers!
Dave G.