In my opinion, the factory 'precision' is a lot better than people give credit for.....
And when I hear, comments like my deck was out 0.015"......yeah right.
Two simple examples bear this out:
- Mopar main brg caps are indented to the block on V8s. A snug fit, might need a tap to insert. Half a thou too tight, doesn't fit; half a thous too loose, drops into place.
- cyl head dowels. Half a thou out, & head needs 'help' to fit over dowels.
Using the 'common sense' derivative, why would other machining operations that are less obvious than the above be less accurate?