Mike, at first I had a master and slave cylinder of the same size. Clutch was near impossible to release.
Then I moved to a 3/4" master and a 7/8 slave. The result was only a little better, still way too stiff clutch. I even tried a 1.5" slave cylinder from a Mercedes truck with the 3/4" master, now the clutch release pressure was ok, but of course the clutch was only engaged about half when the pedal was fully depressed. I calculated it would take a 3/4" master cylinder with about 3 - 3.5" stroke to fully engage the clutch with this slave cylinder. I couldn't find something like that, besides this pedal travel would be about a mile with this long stroke master cylinder.
I tried several clutch cylinder combinations, relocated pedal assembly and installed longer clutch pedal, and changed the long style pressure plate to a less aggressive diaphragm style. And as Mr. Fixit and trularin said the throw out bearing also is not the problem.
This leaves only the clutch disc and the clutch fork. I don't know what else would cause this problem.
AFAIK the clutch disk itself has no influence on clutch pedal effort.
What about the others who have toploaders in their Cobras, do you use the stock clutch fork, with cable setup or hydraulics/McLeod hydraulic TO bearing?
Did anyone else ever have a problem with the stock clutch fork? Are all toploader clutch forks the same length? Can a clutch fork that's designed to work with a z-bar linkage ever work right with a cable at all?
I really appreciate any help!!