You need to get an old motor manual and study the Bendix Treadle Vac system as it is nuique. Ford and GM both used this unit in the late 50's and early 60's. I think your problem might be a broken or stuck spring in the rod that goes into the m/cyl. There is a rubber thing on the end that goes into the cyl and on the other end is a spring that controls a valve that gives feedback to the pedal. This info is all from "old memory" so you better get an old book and study.
