I don't understand why you would sometimes lose power instead of gain.

 

not enough pressure in the cylinders

 

Big cams usually = duration = overlap (both valves open) = lower dynamic (not static) CR (which even lower than b18b1's 9.2 sometimes); goto team integra.net site for an article that tells you how to calculate dynamic CR from cam profiles.

 

Think about it this way:

A bigger cam allows more air and fuel to enter the combustion chamber pre-compression. Your car makes all its power based on getting large quantities of air and fuel into the cylinders, compressing said gasses, and evacuating the spent remainder in an efficient fashion. Lowering your compression doesn't allow all the extra air and fuel that your cam is allowing to be compressed to its fullest potential, therefore you're not gaining as much power.

Higher compression = more power. Period.