A Cadillac 500 head, opened up for 2.25" intake and 1.94" exhaust valves. The throats are opened but no seats are cut yet. Notice the shrouding around the bore side of the valves. This needs to be opened to the head gasket edge, but not until the gasket would be unprotected by the head.
The next few images are a Rotax RV case and cylinders. You can see the relationship of the ports. The red lines are areas that needed more work.
These next views show some of the relationships the parts have when
assembled. This one is down the intake tract, notice there are no
obstructions to air flow, unlike a reed cage. Another view down the intake tract. The crank cut aways even help open up
the flow area. You can also see the brass wear plate I installed.
These 2 pics show the cylinder
base and upper case assembled.