Originally Posted by curtis73
Regardless of how GM does it, you won't be able to rehone your block without going oversize in some way. The block was honed to fit your pistons, then the rings wore it larger, then honing it again will make it bigger yet.
The deck should be checked for flatness, but if you don't need to shave it, don't. No need to make the decks thinner if they don't need to be... just like you're not anxious to overbore unless you need to. With flat tops .020 in the hole plus your .015 gasket will make a nice tight quench.
Most good shops wait for the pistons to come in so they can measure that specific set and do final honing for your pistons.
It's important to have the decks square to the main line and a true 45 degrees from the cam and crank center lines.
We have seen blocks that shops bore off an unsquared decks and in most cases if the block won't go .060 because it didn't pass a sonic test its know junk.
If your going to have a block machined for performance use do it once right as it makes for a much better running engine in the end.
Ther are a lot of shops out there doing shorty work because thay don't have the proper equipment to do it right, Don't get me wrong building a bone stock engine you can get away with a lot but building performance engines the substandard machine work will show up after a while.
There is a right way to do things and I guess there is a semi right way LOL.