Here is the 363 " hemi" and the other more common looking version.
The Hemi is nothing special as built.
It requires loads of welding and tinkering to make it flow.
I have been working at one off and on for years.
But that block with the that piston is the jewel.
Any Honda or standard clone head and cam will fit it.
SO replace that 26cc hemi with a 14cc clone head off a GX160 chinese made 5.5 hp engine and you have a huge compression increase.
This is 730 predator with its dished piston.
Still a good motor but the dowel pins are larger on it so you have to remove them and eyeball the 14cc head in position.
You loose a little compression but more importantly ( to me at least ) is the flat top works with the 14cc closed chamber head to make a nice quench area for good mixing.
This is handy in an application like this with slow burning lazy fuel.
Both styles of engine use new larger valves.
If you have access too it some of the other 208cc clones also have a nice flat top pistons that will work well with the 14cc head.
But you have to watch.
I buy a lot of engines to see what's inside and if I do not like what I see I carefully put them back together in running order and return them.
No harm no foul....