- Apr 5, 2003
Man, 12mm seems huge. You'd have to greatly enlarge the hole on the manifold. Then is the 12mm nut going to spin on and clear the rest of the manifold casting? If it were me, I'd do what Bryan mentioned and weld it shut and re-tap. Option #2 would be some sort of insert that allows for a smaller stud. Either way, I don't think 12mm is a good idea.