what size bolt plugs california emissions holes?

[Chubie]

What size bolt/thread plugs california emissions holes in exhaust manifold? Thanks
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[CJ]

Those holes aren't regular thread, thy look like 1/2 NPT (national pipe thread). Could be 3/8, 5/8 or even 3/4 but it's hard to tell by the picture. Doy you have what was in there? If so just head to the hardware store and look in the pipe plug section.and compare. Also, can you post a picture of what was in the hole so we can be sure.

 

[Chubie]

I am being told 3/8 national pipe thread.