Originally Posted by vpiuva
These guys are thinking in reverse.
Your Campy would be ISO, and if you tried to put it in a JIS frame it would be very difficult to do so because the ISO is bigger. Your frame has a problem, or your cups have been worn or modified. You need a good set of calipers to tell what is what.
I believe th OP is talking about a standard headset and that the cups drop into the head tube without needing to be pressed in. Althought there is a difference in crown races I don't believe there is a difference in the ID of the headtube.