Obviuosly it depends on how much has been skimmed off, but I just wondered how much difference it actually makes?
If say you take an average head skim thats been done not because of damage to the face but just a routine skim as you would do when building up a new engine, and the same for the block is it actually enough to measurably effect your CR?
Will it for example increase 7.5:1 to 7.6:1 or 8.0:1 or is it nothing really measurable?

Cheers!