Valve cover issue

Buckeye Fan If those "cracks" as you call them are identical on each valve cover, and they do look like they are identical, that's just a defect in the mould for the casting. Clean em off real good with a wire brush and some lacquer thinner, and look at em real close, I would almost bet a paycheck those are not cracked, but small amounts of raised excess aluminum from an irregularity in the mould. If you dont have the centers of these knocked out for breathers on that side of each cover, and it looks like you dont, then you dont have baffles screwed into those bosses either. Theres nothing there to crack anything