Plug smog holes in exhaust manifold 83 Hurst

[hajnovak]

Does anyone know the thread size and proper material I can use to plug the smog holes on my 83 Hurst/ Olds. Thanks for any info it's greatly appreciated. Mark

 

[DoubleV]

They have dedicated plugs for those but 1/4" pipe plugs work good too and you can get them at any hardware store. Brass is better, but it doesn't really matter.