I am eliminating the smog stuff on the balance tube on the intake manifold of my 1970 Z. I want to put a threaded plug into the larger hole near the PCV valve and in one of the smaller vacuum barbs on top of the balance tube. Standard NPT 1/4 and 1/2 plugs look close but do not work. Anybody know the correct (?metric) thread size for these openings?

Mike

We plugged most of the vacuum ports on ours and I recall using some 3/8 NPT plugs.

Run the holes with NPT taps and they'll readjust the threads just fine and NPT plugs will work...... just fine. Maybe ad a spot of sealer.

In the words of Gunnery SGT. Thomas Highway "You have to learn to improvize, adapt!

Search here for BSPT and you fill find the exact sizes, but as Bruce says, and as I have done just about everywhere, run an NPT tap into them then use an NPT plug.

The recent thread I remember mentions Grainger and maybe McMaster Carr as sources for BSPT fittings if you must do it "right"

Thanks Guys, all good advise.