Have raised this before, but had no definitive solution.
Not sure why they are different combustion spaces.

My main query is, if I use the one with some fins missing, (one on the right- both pics)what is the limit before it is classed as scrap? Can probably get some rebuilt, cast welding done. But just wondering if these would be near the limit, seems not to be a third of the fin cooling area at present?

This is my Cast iron head, along with the spare cast iron head.



This is the tops of each.



This picture was with my spare Alloy Cylinder head, alongside the unusual combustion chamber Cast cylinder head. It seems to me that the odd one is the one on the right of all the pics. For those who notice, the plug holes are filled with putty so I could check the actual cc of the combustion area, they are the same. However it does look like it will create a different movement of the combustion gases. Not sure what benefit it has.