Using your numbers, and a .022 head gasket, with the 225 stroke of 4.125, the compression ratio is 11.52
Changing the bore to 3.500 the CR comes to 12.09
http://www.wallaceracing.com/cr_test2.php
Increasing either the bore and/or stroke increases the CR. Decreasing the combustion chamber size and/or head gasket thickness, increases CR