The flat (uncontoured) replacement head completely removes all of the patented Ricardo features that made the flathead engine successful. There is no quench surface, no turbulence, just a open hole.
What you see is nothing like combustion in an actual SV engine.
Perhaps panic - but I think you are holding the bar a bit high (then again you always do).
Even if the 'window' head doesn't include all the best engineering features of a side-valve design it does reveal the essential elements of 'flame-front' travel from the combustion chamber into the cylinder - the swirl of the exhaust - and the sometimes foggy intake stroke. And for the me the fact that the super rich alcohol mixture even lit was amazing.
