Exhaust mainifold plugs

I've removed the AIR pump and associated plumbing on my '71 :v6: . What have other guys used to plug the holes in the exhaust manifolds? The threads on the fittings aren't pipe threads. I thought I'd grind down the tubes and braze over the holes on the fittings, but I'm missing one. Any ideas?

 

I took care of those holes using some inset allen head screws. I took a quick look around here for the receipt with the spec but I couldn't find it. If I remember correctly, they were 1/2" x 18 (course thread) and the ones I got were 3/4" long. These were black as well so they blended into the manifold nicely. Use a little loctite red (semi permanent) to seal possible exhaust leaks

 

I'm pretty sure they are 1/2X18tpi as well. Mine are just regular bolts, Nothing special.

 

They are 1/2-13 threads, not 1/2-18 (no such thread). If you can, find stainless steel ones. If you want them to look good use 1/2-13 allen head set screws in black oxided steel or Stainless units if you intend to remove them at a later date. Red locktite is semi permanent and only removeable with a torch to heat up the locktite for removal of the bolt.

 

Be sure you hang on to that smog stuff. There has been more than one member looking for it for passing vehicle inspections in strict states.

 

Thanks guys, I knew I'd get the answer here. The guy at NAPA told me it wasn't a pipe thread. I'll got to the hardware store tomorrow.

 

I used the plugs that are used to plug the auto tranny lines on new radiators.

 

Thanks for all the replies. I got stainless 1/2" - 13 bolts and they worked great.

 

i might be one of those guys looking for the air/smog stuff. let me know if you want to get rid of it.