I have a set of used EB Porting heads and noticed the #4 intake bolt hole (in torque sequence) initially i thought was stripped out, but later noticed it is tapped larger, to a 1/2-13 thread. Now is this what size a helicoil needs to be tapped to, and I just have to put a 3/8 helicoil in, or should I just get a 1/2-13 bolt to use for that hole?

 

Put the helicoil in. Maybe it had one and lost it?