I heard something interesting a few weeks ago. I haven’t had the time to verify it yet but I trust the guy who told me.
This guy had a conversation with Kevin from Ishara-Johnson about crank scrapers, windage trays and the like.
He says Kevin told him not to paint or polish the block.
He said Kevin said that the rough surface breaks up air bubble in the oil on the way back to the pan. A smooth surface doesn’t do that.
Thinking about it I think it makes sense. It’s essentially the same thing as a burr finish on a manifold. Agitating the boundary layer to break up bubbles in the oil is akin to wet fuel running down the port getting reatomized.
Something to think about…