Port size rpm performer manifold question

Duster Duke Boy said
I’m just trying to learn not about not trusting, trying to understand. if I measure hole at 1/2 in how do I know what size npt it is?

Hey no biggie. We've all gotta start somewhere. Good on you for trying to figure it. Besides the photo above, check out a standard drill chart. a 1/2-14 NPT tap uses a 23/32" drill bit (nearly 3/4") whereas a 3/8-18 NPT uses a 37/64" (about 9/16"). I reference the one on my wall all the time.