1\8 NPT - What is it for?

[Avi]

I have a late model engine. There is a 1\8 NPT taped hole on the lower right side of the exhaust portion of the manifold. I assume this is where the exhaust back pressure test gauge gets attached. The problem is that the hole in my manifold does not go all the way through. It seems to be a blind hole yet it had a plug screwed in. What am I missing?

Thank you,
Avi

[msmith10]

I believe that is a water drain plug. It is probably blocked off with crud. Take a screwdriver or similar tool and clean the stuff out of there.

[roadnsky]

Are you talking about the EXHAUST FLANGE (1st pic)
or the DRAIN PLUG that Mark described on the manifold? (2nd pic)

The first pic is where you'd check exhaust back pressure.
But, I agree with Mark, that it sounds like you're talking about the drain.
If so, do what he says and clean it out. A screwdriver and coat hanger did the trick for mine.

[Avi]

Drain makes sense. I'll go see if I can clean it out.