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Discussion Starter #1
I completely removed my smog pump, capped the lines and installed an off-road H-pipe years ago.
I now want to finish cleaning up the back of my engine by removing the thermactor cross-over tube and the exhaust tube running down to my H-pipe, and also removing the EGR system via an EGR delete kit (blockoff plate and EGR eliminator plug).

I was planning on using the cylinder head smog threaded insert plugs from LMR to seal the bolt openings at rear of heads, but heard that these ports can be completely full of carbon build-up, so I was going to use a 5/8"x11 thread chaser to clean the carbon build up out of these ports.

With the thread chaser will that carbon residue go into the engine or out to the engine bay?
Also, if I decide to just block off the holes using a blockoff plate instead of using inserts, is it ok to leave that carbon build up in the rear ports, or is it casing a performance issue?

Thanks!
 

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I plugged the hole with a bolt from home depot. I think it was 1.5" in length. I used thread sealer paste. Came out fine and plugged up well. Heads are back on and its gravy
 

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IF you use the plugs from LMR, and after cleaning the threads with a chaser, use some sort of threadlock when you install them. I had one vibrate out and I lost it on the highway. I have AFR 165 renegades, new when installed.
I replaced both of them with short bolts from Ace Hardware.
IF you're building a show car and will lose points when someone sees the bolt head on the back of the head, go with the plugs. But the bolts are easier and cheaper.
 

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Discussion Starter #5
Great info, thank you for the replies!
I may look at just using bolts instead of the LMR plugs.
To seal the bolts should I use blue loctite on threads (red?), or should I use rtv copper?

I also saw these smog block off ports at LMR which would be an easier install, as they re-use the thermactor bolt holes, and they have a dowel to line up with smog port openings:
 
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I have a set of those threaded plugs from Ford and they come with sealer on the threads. You can also start the engine before you put the plugs in and blow out any loose carbon build up.
 

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I have a set of those threaded plugs from Ford and they come with sealer on the threads. You can also start the engine before you put the plugs in and blow out any loose carbon build up.
Do you think starting the engine would blow out a really severe build up? Mine is so bad I had to dremel the first 1/4” of build up to make a dent.


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If you are blocking the hole and ultimately the flow through those ports, it really doesn't matter if they are cleaned out or not. If just chasing the holes, then sure, hit it with air or grease the tap to pull out the debris.
 

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I actually found a different set of covers that use the original tube mounting points. They’re stupidly expensive at $39.99, but solve the problem without hours of work trying to clean out the buildup.

-Update: I found what Zak88lx mentioned.


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