What thread size are the smog fittings?

[JEFF]

I bolted a new header on today ! I put a 280 head

on a 240 block so i'm not using the smog hook-ups.

I need to plug the holes in the header. I tried 1/2" NPT

in one hole - no go. The larger hole is to big for 1/2"NPT,

but to small for 3/4"NPT. Any idea what size these two

holes are??

- Jeff

[catorres_78]

I'm wanting to do the same, did you figure out the size?

Thanks

[Arne]

I don't know the size, but the threads are BSP (British Standard Pipe), not NPT.

[Hunter260Z]

I don't know the correct size either, but take your old manifold by NAPA. They have plenty of plugs. Mine have been in app.10 years. No problem. Go ahead and pick up 8plugs, this will come up again.

[Hunter260Z]

I had a spare plug in my toolbox. The plug is 18 threads per inch.