Quote Originally Posted by staysikwitit
"using a 100% stock (undecked, standard bore etc...) GSR block and a 100% stock (unmilled, standard valves, combustion chambers etc...)PR3 head:

USDM ITR(P73-A0) = 10.8:1 compression (no shocker there)
USDM B16A(PR3) = 11.03:1 compression

Now here's where it gets interesting...

JDM B16A(P30) = 11.24:1 compression (dome is 6.93cc)
JDM ITR(P73-00) = 11.32:1 compression (dome is 5.96cc)"

http://www.honda-tech.com/showthread.php?t=1783523

don't know if thats 100% correct, just my attempt at helping you, lol.
so according to that, if its a usdm b16a head, the ratio is 11.03:1
and if its a jdm b16a head, the ratio is 11.24:1.
damn! it would jump to mid 11s? i wanted to do a factory rebuild with keeping the b16 head. and maybe boosting it sooner or later after. hmmm maybe it would be a good idea for a thicker head gasket? i kinda wanted to stay around the 10 ratio for a decent NA and better spool once i boost.