I found this thread very informative. Most poeple on another forum Im dont understand that as the clutch wares, the fingers move outward and thus the spacing of the internal, and even external are important.
I have a bit off install here, and am putting a GTO T56 into my 940 Volvo. From the reading and video watching, Im apt to stick with a 3/4 master. I have a 6-1 pedal ratio, but since I have a 240mm clutch (9.5inches) I bet my mecahnical ratios are different on the Pressure plate. Southbend is saying .250 for disc release and something like .4 inches compression on the fingers for proper disc spacing.
I need to replace my master in my car, and was looking at the 7/8 bore setup....but looking at the overall picture, Im thinking its best to start with a 3/4 bore again.
And I love the way you do things....Ive cut up used heads for porting before to see how much material was there, but never anyting new....I love it!