318 heads, 302 casting. Mystery holes?? (Solved!)

Righty Tighty said

Thanks guys. Turns out they’re the same pitch and diameter as the valve cover studs. Rusty, is there any particular reason you tap them to 1/4-20?

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If they are the same as the valve cover fasteners, someone has already tapped them to 1/4-20. And yes there's a reason I tap them. Because they are not tapped from the factory.