I thought I seen it in a book somewhere. I asked my builder and he showed me a block he had and what to clean up.

I don't have any casting flash on mine though. Would it still be worthwhile to smooth out that area by the 2 oil return holes?

 

I stand corrected, I just looked, there's 2 large ones at the back, and 8 more small ones in the lifter valley near the tops between adjacent lifter bores...

I'm about 1/2 way done, I'll show the pics when I'm finished. Might not even make any difference, I don't know. I figure whatever helps oil get back to the pump quickest is good.

Does no good sitting up in the lifter valley.