I'm sure this will rattle a few cages - oh well. Setting the block deck height to set your quench/combustion chamber/piston clearance is important, as eliminating mechanical interference and checking compression is again, important. Decking a block solely to square it up? More important to help make the intake seal than anything else - don't waste your time or money if you think there's "magic" power there. There probably isn't 5 HP gained by decking the block just to square it up, since most blocks aren't that far off, usually in the .010 range, and cutting only .010 off a block won't change compression enough for a big power gain. You will get the same power increase by a thinner head gasket. So if you are cutting the block to set piston to deck height - whack away. Otherwise there isn't the gain there by trueing the deck to the mains that lot of people seem to believe. I've heard of a lot of people decking blocks, but not equalizing combustion chamber volumes - HUH - whats the difference? Ones just promoted better I guess.