Without going into a lot of detail in this post; but when changing the stroke of an engine, the relationship between crank throw, connecting rod length and piston/pin design all impact the process as well as the end compression ratio.
A good read on the subject is:
http://www.hotrod.com/how-to/engine/...ke-any-engine/
A bit heavy on tech, but it does answer most of the questions someone new to the process would usually ask.
DB