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Two main problems.

Problem 1 is they keep loosening up. Not finger loose but definitely looser than the torque specs when I put them on there. I know you can't use loctite or a lock washer. I've heard about special locking nuts they make for some cars but I don't know where to get them and I don't want to wait for them to arrive in the mail. The stud goes into the head and then a nut goes on the stud to hold the manifold in place so I don't think doubling up on the nut would do anything. Any other bright ideas?

Problem 2 one of the stud holes stripped so I tapped it with the same diameter and pitch to repair it. It worked but the threads suck and the stud doesn't lose its play until it's 90% into the hole and I can see carbon escaping from this area on the gasket. So I think I need to retap one size up. But I'm concerned I'll run into issues with the larger stud being longer and not seating right. Thoughts on this?

Thanks bro

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  • Why can't you use Loctite? I wouldn't if I didn't have to, but if you can't keep them tight any other way...
    – GdD
    Commented Mar 7, 2022 at 10:18
  • It's on the exhaust manifold.
    – user875234
    Commented Mar 7, 2022 at 10:31
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    Have you checked that your exhaust manifold is not warped?
    – HandyHowie
    Commented Mar 7, 2022 at 11:01
  • I had them resurfaced at a machine shop recently but I didn't check their work and there may be some warping. I'll have to check. There is still a little warping near the outer edge of one stud hole. Warping tolerance for these is super small, right? I don't see a gap, especially after the gasket is installed. Maybe part of the problem is I used gasket maker ("the right stuff", specifically for exhaust manifolds) but the instructions say to install dry. Someone suggested I use a helicoil and ....a special lock nut. Still not sure how a lock nut will help if the studs themselves are loosening.
    – user875234
    Commented Mar 7, 2022 at 11:13
  • So it is the stud that is coming loose, not the nut? How do you know? Is the issue that that you have an exhaust leak from the manifold to head? Not just that the studs are not staying torqued?
    – HandyHowie
    Commented Mar 7, 2022 at 11:35

1 Answer 1

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I would say the most likely issue here is that the manifold surface is not totally flat. Somewhere near is not good enough.

A warped manifold can cause the bolts to snap. For example on my Land Rover Discovery there were 2 snapped bolts I believe were caused by the manifold warping. The new studs you can see in the picture has self locking copper nuts.

I would get it skimmed by a professional. The engineers that did mine only charged about £20 UK. Well worth the money.

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