Amc 304 exhaust manifold repair - JeepForum.com
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post #1 of 17 Old 12-02-2019, 01:33 PM Thread Starter
Bmann412
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Amc 304 exhaust manifold repair

I am cleaning up my exhaust manifolds in preparation for my engine rebuild. I have successfully removed all the damaged studs and almost all of the hollow hex head bolts. Except for one which the head of the bolt is completely deformed. Not sure if I should leave it as is or try and remove it with heat and vice grips. Where can a replacement be purchased and same with the studs since mine are to far gone.




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post #2 of 17 Old 12-02-2019, 03:47 PM
StoneTower
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Do you have a welder? If you do, you can weld a big nut to the rounded head. Soak it in a good quality penetrating oil for a day or two and then weld the nut on. The technique works really well.


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post #3 of 17 Old 12-02-2019, 10:52 PM
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Those are plugs used to block off the AIR injection ports in the manifold after the system has been removed. Most folks use brass. If the one you can't remove doesn't leak, you can simply leave it in there and move on.
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post #4 of 17 Old 12-03-2019, 07:33 AM Thread Starter
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Well I tried heating up the bolt and using vice grips. That wasnít working so I gave welding a nut to it a try but they kept breaking off. Lastly I tried heat and an easy out but that broke off in the bolt. So I call it quits for the night. So I guess I have to resort to drilling it out and re-tapping the threads. Can I use a standard bolt to bolt off the hole or does it need to be brass?


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post #5 of 17 Old 12-03-2019, 11:01 AM
John Strenk
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You can use anything you want if you are going to tap it yourself,

But I think a tapered pipe thread would work best for a pipe plug to put it in.

Look up tap and drill size for a tapered pipe plug.

I think the original were straight threads and the tapered plug was just jammed in there.

Is it leaking now??? Just saying.


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post #6 of 17 Old 12-03-2019, 12:28 PM
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Some of the nut welding videos show guys building up the broken stud with a weld before they weld the nut over the nub they create with the welder.
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post #7 of 17 Old 12-03-2019, 01:45 PM Thread Starter
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Quote:
Originally Posted by StoneTower View Post
Some of the nut welding videos show guys building up the broken stud with a weld before they weld the nut over the nub they create with the welder.

I did just notice that in the video. I will have to give that a go when I get home from work tonight. Really trying to avoid drilling it out.

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You can use anything you want if you are going to tap it yourself,



But I think a tapered pipe thread would work best for a pipe plug to put it in.



Look up tap and drill size for a tapered pipe plug.



I think the original were straight threads and the tapered plug was just jammed in there.



Is it leaking now??? Just saying.

I like the pipe plug idea. Unfortunately I am not sure if it leaked or not since i only had the Jeep running for a short period of time 2 years ago. I am sure it will leak now that I have mucked with it.

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post #8 of 17 Old 12-03-2019, 02:02 PM
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You can get as pipe plug tap a Harbor Freight.
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post #9 of 17 Old 12-03-2019, 06:04 PM
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Why try to restore old cast iron exhaust headers? Why not just get some aftermarket tubular headers for a bump in power and easier installation? If smog is an issue, get some that are smog legal. They exist. I converted my CJ7 back in 2002, no problems there.
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post #10 of 17 Old 12-03-2019, 08:36 PM Thread Starter
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Current solution. Ground it smooth and confirmed it does not leak by blowing compressed air directly behind it. Tried welding a nut again but the bolt would not budge and ended up snapping the nut off. Once itís painted no one will ever know the difference. If they start to leak I will either find factory replacements or look to aftermarket headers. If there are any objections to my current solution please let me know.

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post #11 of 17 Old 12-04-2019, 12:06 PM
John Strenk
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Good that it doesn't leak. Saves time.

Is that brass or steel?

Looked like brass in some shots and was wondering how you welded a steel nut to a brass plug.

Kinda makes you want to cut off the other ones and file it smooth doesn't it....


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post #12 of 17 Old 12-04-2019, 12:26 PM Thread Starter
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Quote:
Originally Posted by John Strenk View Post
Good that it doesn't leak. Saves time.



Is that brass or steel?



Looked like brass in some shots and was wondering how you welded a steel nut to a brass plug.



Kinda makes you want to cut off the other ones and file it smooth doesn't it....


I thought it was brass which might have explained why I had trouble welding nuts to it. Until I broke the steel easy out in it lol.

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post #13 of 17 Old 12-05-2019, 11:03 AM
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I can't tell from the picture. Is it brass colored or steel colored when you grind on it? Will a magnet stick to the other plugs? You cannot MIG weld a nut to brass...
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post #14 of 17 Old 12-05-2019, 11:37 AM
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Those bolts are standard 9/16" x 18 thread count. I couldn't find any that were short enough, so I cut down 1" long bolts.

I agree with John, the OP probably jammed NPT pipe plugs in there. In which case, the threads are already ruined, and it's probably best to leave it in there, as you did.

Matt
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ManifoldPlug4.jpg   ManifoldPlug5.jpg  


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post #15 of 17 Old 12-05-2019, 06:19 PM
StoneTower
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Wow...using grade 8 bolts as hole plugs. The little 5 line star on the head does look fancier than the 3 line star...
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