ARP Head stud nut clearance with valve springs

69_340_GTS said
You can't have a 1/2" stud with a nut that takes a 1/2" socket/wrench. Per ARP's catalog their 1/2" 12-point nuts take a 9/16" or 5/8" socket.

That's why I said I think. I would have to walk out and grab one. When you are my age, 1/2 and 9/16 are so close you just lump them together.

Now that I think about it, the 1/2 size is for 7/16 rod bolts with 12 point heads.