True, there is no "cave" carved out left to right like on some egnines. Any idea why some do carve out a cave and others don't?

Of course, there is more space/volume in the case for fuel/air mixture, but that still does not answer why some do and some don't make a cave/enlargerd chamber.

In my oberservation the following modify this area to the maxiumum: Max Power, Capricorn and Mag

And the following do not: MH, Murnan, JP, IDM mods, Nova tuned, OS tuned. These guys do carve out/grind/polish the existing channels like in pic 14, but they do not carve out the whole chamber area left to right.

Fuel consupmtion could be one reason, max or optimum scavenging could be another -- but anyone got an more substantial ideas why some do and some don't do this? Lets hear them!