"hot or not"
I have the heads #1 in an engine that will go in probably some time in July. The combustion chamber is very close to stock 928 chamber, so no surprises expected. The only combustion chamber difference is that there will be a bigger dish on the piston to lower the compression ratio.
I just bought the heads #2. Those have some welding effort in the combustion chamber, and the biggest valves that one should fit in (without putting in oversized valve guides and offset boring the intake guides to move valves further from each other and offset boring the exhaust guides to change the exhaust valve angles to get them further away from the intake valves). The combustion chamber shape was informed by what was learned during a project relating to one Honda IRL engine.
Heads #3 are a random picture from the internet, it's some motorcycle head, probably some 750 cc single cylinder. It appears to have slight radial valve angles as well.
If cylinder heads are ranked based on voting, someone else got the winner!
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]