Whats the difference between open & closed chamber heads?

Last I checked, the combustion chambers on cylinder heads are both. They are open when pulling in air, or expelling it, and closed when not. Where did you get this from?

Us old scool chevy guys used to throw that term around alot. Never really heard it in a Ford context though. But for exampe, some big block Chevy heads in the 60's and 70's were "closed chamber" meaning that the combustion chamber size was very small to increase compression. Problem was that it hindered the flow some because the valved were more shrouded. The open chamber haed is just the opposite with a larger chamber. You could tell them apart because on the closed chamber head, instead of being basically round the chamber was sort of figure 8 shaped.