plugging this port on headers

[TechNova]

That plug doesn't look like it is threaded in very far, could be wrong threads. Are you sure it screws in a few turns by hand?
Dykem or a Sharpie on the end of the plug will help tell you where it is hitting inside. Put some on the end of the plug, screw it in un til in bottoms, ull it out and see where the dykem is scrapped off.
When I removed AIR systems back inthe 80's I would cut the line at the top of the fitting and braze the hole shut. this would give
me a plug that had the right threads and the proper taper seat to seal. DO you have a yard nearby where you can get a fitting? You can break the metal line off in the yard and use a socket to get the plug.

 

[KRS1]

Hi Yes, plug is fully threaded into all available threads. If you look closely at the picture; the first red sharpie mark indicates the full penetration. I was hoping to get a few sensors when I went to the yard Friday..but all the trucks from the 88-94 vintage didn't appear to have any sensors. It would have been the optimal solution. I found one with a plug already installed but it looked really rusty and I figured I already had fresh ones coming...Perhaps from 88-91 or so???It seems like they only used these ports for a few years?

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[Mr Eric]

Just about guaranteed to be the wrong plugs, even if the thread size and pitch is correct.

What sealant do you plan to use that will stand up to exhaust gas temperature?

Cut the plug down, so that shoulder engagement happens.
Then use high temp anti-seaze, I have a bottle that's rated for 2400°f. This will fill the threads enough that service seal will occur.

 

[KRS1]

Cut the plug down, so that shoulder engagement happens.
Then use high temp anti-seaze, I have a bottle that's rated for 2400°f. This will fill the threads enough that service seal will occur.

I ended up finding a old tube (about 1/8 full lol) of muffler cement to seal the threads. I figure it would work as well..I cut the plugs down and screwed it in. I will have to wait awhile to see if it seals (budgetary situation) to finish buying the components to start the engine.

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[Supercharged111]

I would have just slapped a copper washer on there to do the sealing.