hi there i was wondering if i'd be able to work out my engins comp ratio without stripping it ?

i know that it has 4x4 low comp pistons, cometic 3 layer gasket, the head has been matched at 49.9cc, and is standard bore the only thing i'm unsure is if block has been decked.

i prob need to know other info as well so any help would be really helpfull
and if any1 knows the formulas

cheers tony