Head cc

I just CCed a set of 291c and a set of 090 heads. They both came out to 58 cc. I did them both twice. Is the "accepted" info that the 291 is 50.88cc and the 090 58cc incorrect? Has anyone else done this to confirm or deny my findings?

Just some larger valves installed but I would think they would make the chamber smaller. 

The sides of the combustion chamber near the sides of the valves are in as cast condition. I'd like to know if others have cc 291c heads and what they came up with. It seems odd that AMC would redesign the head and one year later do it again.

I doubt untouched 291Cs would be 7cc over nominal spec.  That's a huge difference.  I did a set like shown in PAS and IIRC they ended up at about 58 CC.  

Ii think I found where my extra cc came from. I dragged out an untouched 291 head and CCed that, it came out to 54cc. At closer inspection I discovered that the valves are recessed further in the heads and the larger valves are noticeably more concave than the stock valves. The combustion chambers are untouched. Funny thing is I always thought I had 11.7 compression ratio on my 68 390 but with the newly discovered 58cc heads I actually have considerably less. That combined with the less lift then what was advertised on my cam confirmed by Delta Camshaft I always wondered why my car would "only" run 11.70. Moral is you take nothing for granted and check everything.