RichJames & Cat302 I think you're answering a different question.
Lightspeed was asking about the spirals machined into the underside of the covers - not the tool marks. I suspect those grooves are to enhance the heat transfer properties by giving more surface area for the hot oil to splash against. Simple as that I believe. Although the designer may also have been trying to make the roof of the cover thinner while leaving the spiral ribs there for strength.
That said, I seriously doubt there's much cooling to be had with them vs. the stock covers.
Last edited by truckin-on; 10/02/22 10:16 PM.
