Advice for drilling on my intake wanted.

Rug_Trucker said
I tried to open up the big hole for the head pipe on a exhaust manifold with a bur and die grinder. Same bur I used to port the head. I gave up! :(

Yeah, the exhaust alloy is more difficult, but fresh carbide still works, I ported a set of mid-'70's 440 units. It does go sloooow tho',.......