Paul,

I am going to agree with you on the following:

"Rarely does a B20 block need a hair cut, that money used would be better spent doing more headwork." But with a couple of qualifying comments.

1) The money saved from not having the block decked will not buy much head work.
2) You have to check each block to know which ones really do need to be decked.
3) Although some blocks technically do not need to be decked, engine performance will benefit from decking either to make sure the deck is parallel to the main bearings and/or to reduce the squish distance closer to what is optimal.

When doing our performance engines we check the deck height on all of the blocks and bring them all up to the same spec so that each customer gets an engine as good as the others. If we are doing the machining on a customer's own block and he/she wants to save money by not doing it, then that's fine.

Yes, I was surprised to find a few blocks with .030 deck heights.
We have had customers report the same on their engines.
After 40 years I cannot necessarily tell whether those engines have never
had any work done, but it appears to be so. Since most blocks seem to be in the
.005 - .015 range, and we have found a few at or near .030, I have wondered whether there was something different about the combination of block, pistons, and rods used in those engines.

John
V-performance.com