I am partially rebuilding the B18B engine in my 65' 1800S. After much research I plan to upgrade it to basically the 67'-68' 1800S spec. (approx 118HP) So that means a "C" grind cam, a small raise in compression ratio, dual outlet type exhaust manifold and some "KD" needles in the twin SU's. Seems easy enough and i have a very solid lower end (rebuilt in 1990) I checked compression before pulling it out and got 214-217 PSI across all four cylinders, seems healthy. Upon dis-assembly and measuring to see exactly what i need to do to get the 10.5 to 1 compression ratio i have found what seems to be a semi low compression engine, the specs do not make sense to me. I have the correct for the car high compression head (86 mm thick) and am getting a combustion chamber volume of a rather high 47cc on all four chambers. It does not appear to be ported in any way. Also i have what seems like a tall .030" deck height. If i plug in the factory bore and stoke, this deck height, a .030" head gasket and the 47cc volume i come up with a 9 to 1 compression ratio. I thought this was supposed to be a 10 to 1 engine? even if i zero out the deck height i am looking at 9.65 to 1. My engine actually is already .040" over on the bore which helps the ratio a bit but is something odd about the chamber volume on my head and tall deck height? Also how much would i need to mill the head to drop the 47 cc to say 43cc?