only had 110psi compression on my newbuild wiseco pistons 92.5, but did use a 1,6 gasket. could the gasket be the reason.

engine is back out due to bore wash so got all new rings,also blocks new due to damage, new crank as iv changed to center thrust.

would a 1.3 mm gasket be better?

how do i work out compression ratio before i fit anything.

 

The low compression could be down to the bore wash tbh.
As for the compression ratio, look for a CR calculator online and plug your measurements into that to work out your static compression ratio.
Depending on your piston compression height/cylinder head volume/deck height etc etc, i would imagine your CR would be in the region of 8.0:1 to 8.2:1 and if it is, thats fine.

Fitting a thinner gasket would up the CR a little but would also reduce the safe quench.

Mick