There is a formula for this. Read this link and do the measurements and calculations. Each time you shave 1cc out of the chamber it changes it's configuration and you should do the calculations all over again for the next cut.
Since combustion chambers have a different shape depending on the casting family it's hard to make a generalized statement.
http://www.eatonbalancing.com/blog/2...1cc-reduction/
There's a chart that will put in the ballpark at the link.
Dale