New clutch setup won't disengage
Since I have only 3/4" fork travel currently, and the clutch is just barely dragging enough so that I can't get the trans into gear with the engine running, I estimate I need 7/8 to 1" of travel. The available stroke is limited to 3/4" unless I make other mods as we discussed above, which I'm trying to avoid. So I need to decrease the fork ratio at the new hole by a factor of 3/4 (so that 3/4" of slave movement causes the original hole to move 1".
Pics of similar forks:
(A-body)
Brewer's Performance - Mopar A833 4-Speed Transmission and Component Specialists
This one is 12.5" overall length, or about 12" hole-pivot-TO. From the pic I'm estimating it's 2:1 ratio (4" pivot to TO, 8" hole to pivot).
(B-body)
Brewer's Performance - Mopar A833 4-Speed Transmission and Component Specialists
10.87" overall, again looks like 2:1 in the picture. I think this is the one I actually have, not an A-body fork. Will try and get a more accurate measurement next time I have a chance to work on the car.
Anyway, the new hole would then have to be closer to the pivot by 25% (1/4) of the original hole-to-pivot distance to get 1" travel from a 3/4" stroke. If that distance is 7 or 8 inches, the hole has to be relocated 1-3/4" to 2 inches toward the pivot! Half an inch won't be nearly enough. The fork is stamped into a C-channel shape and it looks big enough to drill a 5/16" hole anywhere I need it. (Nut will go on the flat side towards the front of the car, since it's a pull cylinder).
I may try 1" closer(12-15%) and see if that's enough. Unless there's an error in my math...
There are similar 7/8" master cyls that look like direct replacements. Going from a 3/4" to 7/8" piston makes it (.875/.750)**2 or 36% more piston area. That's about right to go from 3/4" stroke to 1" stroke, since 1/4" is 33% of 3/4... hmm... still more work than relocating the hole though.