Well, I managed to disassemble the top end, finally!

Got quite a surprise when I found slightly domed pistons. They appear very much like the Speed-Pro Forged Pistons L2300NF. Was expecting flat tops. Given
the #063 heads with these pistons, I'm thinking about 9.5:1 compression is pretty close. Using Engine Compression Ratio (CR) Calculator with this data:

bore/stroke : 4.125/3.76
Gasket thickness: .044 -- Not measured just taken from online sites
Comb Chamber : 101cc -- Not measured just taken from various online resources
Piston Dome : 11cc -- conservative here as I don't know for sure what pistons these are.
Deck Clearance : 0 -- ??

...we get compression calculated to 9.3:1


I'm interested in your opinion whether this calculation seems ballpark correct for this engine and whether you all have suggestions for bringing it closer
to reality ( how to measure the cc of the piston dome perhaps or get the deck clearance properly measured for instance ).

Also still in need of machine shop advice and some cam suggestions as well given my intended use and this new data here.

Much appreciated,

-unix