Smog hole plug

[5l32v4c]

There's a metal tube that goes from the exhaust manifold, just downstream of the 4-into-1 union up into the rear of the engine compartment - it has a plastic cap on top. There's one on each side and I think it's used for emissions testing. I read on a Corvette forum that this is commonly called a "smog hole".

One of my tubes broke and I want to plug the hole by threading a bolt into in. Does anyone know the size of the bolt & threads? I could not find anything that would work, metric or imperial.

[honerboys]

if I remember correctly I think it might be a pipe thread or a flare fitting

[5l32v4c]

It's an M14 x 1.5 bolt.

[Sapientoni]

just put a steel ball in it instead of a tubing and tighten the flare nut onto the steel ball. permanent.