difference between 5/8 & 3/4 clutch master cylinder

[vector1]

i was bleeding the clutch today to check operation and after we finished i could not get the clutch to release. i know (at least i think i know) all the clearances were correct and everything was put together properly.

we could not get the pedal to release the clutch no matter how hard we pushed, and the bottom of the bellhousing is cut out so we could look at things, but couldn't see where the throwout bearing contacts the pressure plate.

there is a 5/8 cylinder installed now, tilton setup, and jbl specs a 3/4. the 5/8 worked fine on the previous clutch setup which looked to be otc, and this setup is an 8", so it should take more pressure.

my question, is there that much difference in cylinders to make one inoperable? i could have broke the pedal before the clutch would have moved, or it felt that way.

anyway, i don't want to pull the drivetrain so someone give me the straight scoop, or maybe i will have to pull it. i will be replacing the cylinder before i go any further though.

thanks for sharing.