Exhaust header stud reinstallation issue

[usinjin]

Hello Mafia, for those of you who have replaced their exhaust manifolds with catless headers, how did you reinstall the header studs? I've seen many forum posts about how to get them out of the block, but not many posts on reinstalling. I just got my second set of headers in place (first set had bad welds), including new OEM gaskets, nuts, and studs, but am having a difficult time getting the headers bolted to the block.

My issue is that the header studs do not want to stay in the block while I tighten the nuts. They are backing out as I tighten each bolt. Some of them I can get in about 50% of the way or so and get the nut tightened to spec. I can't reinstall the studs without the headers in place, because the space is so tight I can't slip the headers over them. Double nutting proved ineffective. I might try that again though.

I'm almost thinking about JB-Welding the nut and stud together in the right place so that the stud can't travel backwards and screw the whole thing in like that. Bad idea?

[ZHPizza]

Yeah, it's a bitch. I think I put my studs in with loctite and let them sit for 24+ hrs before installing the headers. Either way, I said to hell with the standard studs and used these N54 studs that were recommended in a lot of the header threads. Made install much easier.

https://www.fcpeuro.com/products/bmw-exhaust-manifold-stud-11127593376

[usinjin]

Yeah, it's a bitch. I think I put my studs in with loctite and let them sit for 24+ hrs before installing the headers. Either way, I said to hell with the standard studs and used these N54 studs that were recommended in a lot of the header threads. Made install much easier.

https://www.fcpeuro.com/products/bmw-exhaust-manifold-stud-11127593376

I saw those but was afraid they weren’t going to fit properly. But if they worked for you, I’m tempted to throw all these troublesome ones out and go for those. Why can’t all the studs look like that?!

[ZHPizza]

I saw those but was afraid they weren’t going to fit properly. But if they worked for you, I’m tempted to throw all these troublesome ones out and go for those. Why can’t all the studs look like that?!Worked for me and dozens of others. Definitely use them if you can wait. One of those little updates that were made on the e90 production run to help the line build these things faster.

[usinjin]

Worked for me and dozens of others. Definitely use them if you can wait. One of those little updates that were made on the e90 production run to help the line build these things faster.

Done. Seems to be a far better solution than trying to mess with loctite. Thanks for your advice!

[usinjin]

Worked for me and dozens of others. Definitely use them if you can wait. One of those little updates that were made on the e90 production run to help the line build these things faster.

Hmm. After maybe 10 hours of tedious wrenching, the new and improved header studs are in. Now, I am unable to tighten the nuts sufficiently. None of them get tight. They screw on up to the flange, but will not tighten against it. The nut strips, or the stud begins stripping out the block. Not fun at all. Nothing seems to be cross threaded; nothing is going on at a weird angle, and everything is hand-tightened before wrenching. Any ideas? This one has me stumped.

[ZHPizza]

Hmm. After maybe 10 hours of tedious wrenching, the new and improved header studs are in. Now, I am unable to tighten the nuts sufficiently. None of them get tight. They screw on up to the flange, but will not tighten against it. The nut strips, or the stud begins stripping out the block. Not fun at all. Nothing seems to be cross threaded; nothing is going on at a weird angle, and everything is hand-tightened before wrenching. Any ideas? This one has me stumped.

Man I've just gone through all of my pictures from that project and didn't leave myself any clues as to what I did. Probably torqued the studs into the head with loctite, then came back 24+ hours later to mount the headers. You said the studs themselves torqued down ok, so the holes in the head aren't stripped right? That's bad news bears if so.

The nuts themselves are stripping???

[usinjin]

Man I've just gone through all of my pictures from that project and didn't leave myself any clues as to what I did. Probably torqued the studs into the head with loctite, then came back 24+ hours later to mount the headers. You said the studs themselves torqued down ok, so the holes in the head aren't stripped right? That's bad news bears if so.

The nuts themselves are stripping???

It's so hard to tell what the issue is. My gut feeling is that the slightly crude fitment of the headers and construction is the root culprit.

The first clue that something was off was that the studs were hard to get in. That made no sense. I examined them carefully and the threads are exactly the same as the stock studs. Only one of them would go in all the way. Again, started each by hand, made sure each one was going in straight. I thought they probably would still be fine, as they are in the block very tightly. None of them stripped at this point.

With the headers on (the hole spacing seems fine, no pressure on the studs), I began tightening the nuts. Brand new, OEM, pert number 11721437202 which matches realoem, even for the newer studs. The first few turns were easy. Then, they got a little harder to turn, and getting closer to the flange, either the nut threads begin to strip, OR it began turning the stud that it's on. When that happens, it starts hurting the stud holes in the block. Yes, one is definitely damaged. Not gone, but not great either. Bad news bears indeed.

So essentially I can't get the nuts very tight. When I try, it starts destroying everything. Wish I had an engine hoist. And a lift.

[t.er]

That sounds really odd... are you sure the stud isn't just turning into the block more when the nut catches onto it? Even if the studs aren't fully bottomed out, as long as you have them threaded in a decent amount they shouldn't strip.

I've dealt with some pretty janky headers myself and a few other guys made up for a CBR600RR and we threaded in the studs as far as they would go by hand. With dirt and other crap blocking the threads, not all of them bottomed out but it tightened up and we sent it

[usinjin]

That sounds really odd... are you sure the stud isn't just turning into the block more when the nut catches onto it? Even if the studs aren't fully bottomed out, as long as you have them threaded in a decent amount they shouldn't strip.

I've dealt with some pretty janky headers myself and a few other guys made up for a CBR600RR and we threaded in the studs as far as they would go by hand. With dirt and other crap blocking the threads, not all of them bottomed out but it tightened up and we sent it

That's what I thought too originally..but then I realized that while turning, the studs were not going in further. And then, one of them got much easier to turn. I carefully reversed it out and the threads on the stud were destroyed. And a bigger yikes when some of the block material came out with it. After blowing the hole out as best I could, I hand threaded in new clean stud. This time it stopped entering the block sooner and I could get it even less tight than before. At this point I stopped, because something is definitely wrong.

The last headers were far easier to install, except the welding was so bad that they leaked right in the middle. I feel like the fitment of these might be too janky. I'm planning on taking it to the indy for a look.

Maybe I should know better than to go for $150 headers.

[ZHPizza]

Man I'm hurting for you here. I can't think of why the nuts wouldn't thread onto the studs correctly. Are they deformed thread locknuts?

I was going to ask if you checked the flatness of the header flange, but that should only affect the seal, not the nut/stud interactions.

Mine were far from flat until I ran them on a flat sanding belt
https://uploads.tapatalk-cdn.com/20201022/585eb9745c99afdd96d61dacb7421397.jpg

[usinjin]

Man I'm hurting for you here. I can't think of why the nuts wouldn't thread onto the studs correctly. Are they deformed thread locknuts?

I was going to ask if you checked the flatness of the header flange, but that should only affect the seal, not the nut/stud interactions.

Mine were far from flat until I ran them on a flat sanding belt
https://uploads.tapatalk-cdn.com/20201022/585eb9745c99afdd96d61dacb7421397.jpg
I’m going to pull them back off today and inspect. Also going to try jacking up the engine slightly and removing the mount on that side. One thought that occurred to me is that maybe the downpipes might be putting too much pressure on them. I had a fitment issue there last time, so I mounted them before doing the final torquing on where they mounted to the block. And the fitment at the downpipes wasn’t very good either. Grr!

I greatly appreciate the suggestions and support.

[ZHPizza]

Oh god yes definitely remove that engine mount and disconnect the rest of the exhaust. This is a good tool to use to support the engine for headers/oil pan gasket/etc: https://www.harborfreight.com/automotive/lifts-cranes-stands/1000-lb-capacity-engine-support-bar-96524.html

Guarantee someone in Austin has one. We all buy it for one job and stuff it in a closet.

I had a fitment issue with the catback section too and ended up needing a spacer. Shit was awful. You end up paying a lot for these cheap headers lol

[t.er]

Guarantee someone in Austin has one. We all buy it for one job and stuff it in a closet.


This is so true, the one I bought is sitting in some house somewhere in Redwood City. And I haven't lived in Cali since 2017 :rofl

[usinjin]

I'd like to thank everyone for their suggestions. I redid the whole thing, and took the time to do it in a more correct manner.

-Removed headers, dropped the rest of the exhaust.
-Jacked up engine and removed mount on the exhaust side.
-Got every stud screwed in completely. Ignored the keyed ends and simply used a nut against the collar to drive each one all the way into the block.
-Test fit the headers on the studs, realized that the 4 corner holes on each header were spaced incorrectly (they were preventing them from sitting flush)
-Redrilled the corner holes using an 11/32" bit.
-Replaced the headers and tightened each nut. This time each one tightened completely. Tightened until I couldn't tighten any further.
-Raised the rest of the exhaust and reattached the downpipes.

Started car. Giant amounts of smoke from behind each header.

At this point I'm ready to trash these as well. I have a suspicion that they bolt to the downpipe flanges so poorly that they are actually being pushed away from the block by the rest of the exhaust. Does that theory make any sense? The downpipe flanges are not in the same plane: one is askew AND the lengths of the headers differ by enough that one flange is actually behind the other by about an inch. (!!)

I'm ready to throw these pieces of garbage away, unless I'm completely missing something. The exhaust gaskets are OEM and are new. Maybe I'll post some pics of the current issues tomorrow?

[ZHPizza]

The smoke came from the header-head connection or header-exhaust connection?

Did you check the manifold flanges for flatness? Mine were bowed so bad they never would have sealed without grinding

[usinjin]

The smoke came from the header-head connection or header-exhaust connection?

Did you check the manifold flanges for flatness? Mine were bowed so bad they never would have sealed without grinding

Header-head. Checked with a metal straightedge prior and they were flat.

[ZHPizza]

Hmm then my only guess would be that the cat back section is prying them away from the head. Hopefully not pulling the threads out.

Did you notch the heat shield on the motor mount? I had some interference there on one of the headers and cut a little bit off so it would fit better.

[usinjin]

Hmm then my only guess would be that the cat back section is prying them away from the head. Hopefully not pulling the threads out.

Did you notch the heat shield on the motor mount? I had some interference there on one of the headers and cut a little bit off so it would fit better.

No interference with motor mount whatsoever.

I'm sharing your theory that the downpipes are pulling it away from the head. Again, the flanges at that end are pretty bad as far as alignment goes.

If it were you--would you try for another cheap eBay set or give up and go for something hopefully better (bimmerbrakes or AA maybe)?

[Galapolis]

You can get some super high quality Schmiedmann headers for only $235: https://www.schmiedmann.com/en/bmw-E46/1943790-new?product=SCM5254MANI

The caveat is that you'd need a custom section to connect it to the existing exhaust. Alternatively, their high flow cat section bolts right up to those headers, and you can buy the full set here for a still very reasonable $641: https://www.schmiedmann.com/en/bmw-E46/16694-new?product=SCM5254

[ZHPizza]

No interference with motor mount whatsoever.

I'm sharing your theory that the downpipes are pulling it away from the head. Again, the flanges at that end are pretty bad as far as alignment goes.

If it were you--would you try for another cheap eBay set or give up and go for something hopefully better (bimmerbrakes or AA maybe)?

I cannot imagine another ebay set will fit any better. They're all shitty. My worry is that the threads in the head were already stripped enough to pull the studs out when you attached the catback section.

Ugh this is a tough spot. Can you try disconnecting the catback section, then re-snugging the nuts on the head flange? I'm really worried that they're toast, but it's worth a shot.

If you can do that and fire it up without leaks, then maybe you could cut through the piping in the catback section (like 6in after the flanges) and drive it to an exhaust shop like that and have them massage the pipes back to fitting.

That's really my only guess at this point. I'm super worried about the head.


You can get some super high quality Schmiedmann headers for only $235: https://www.schmiedmann.com/en/bmw-E46/1943790-new?product=SCM5254MANI

The caveat is that you'd need a custom section to connect it to the existing exhaust. Alternatively, their high flow cat section bolts right up to those headers, and you can buy the full set here for a still very reasonable $641: https://www.schmiedmann.com/en/bmw-E46/16694-new?product=SCM5254

I (of course) have a set of those headers in the garage! I bought them on sale and it came out to about $320 shipped. Really excited to mount them up and should be able to mate them to the rest of the exhaust by changing the flanges out for these: https://www.amazon.com/dp/B0015KZL1M/

I was hot on their full system, but you have to do a lot of cutting/welding to make it work with the 6 speed and people still had a ton of fitment issues. Great reviews for the headers themselves, though.

[usinjin]

I cannot imagine another ebay set will fit any better. They're all shitty. My worry is that the threads in the head were already stripped enough to pull the studs out when you attached the catback section.

Ugh this is a tough spot. Can you try disconnecting the catback section, then re-snugging the nuts on the head flange? I'm really worried that they're toast, but it's worth a shot.

If you can do that and fire it up without leaks, then maybe you could cut through the piping in the catback section (like 6in after the flanges) and drive it to an exhaust shop like that and have them massage the pipes back to fitting.

That's really my only guess at this point. I'm super worried about the head.



I (of course) have a set of those headers in the garage! I bought them on sale and it came out to about $320 shipped. Really excited to mount them up and should be able to mate them to the rest of the exhaust by changing the flanges out for these: https://www.amazon.com/dp/B0015KZL1M/

I was hot on their full system, but you have to do a lot of cutting/welding to make it work with the 6 speed and people still had a ton of fitment issues. Great reviews for the headers themselves, though.

I think my block has probably has had enough torqueing of these headers, I think I'm going to undo these, throw them out, and get a better set. I'm going to assume the threads in the block are okay still, no sense assuming the worst for now. I will get all new studs and nuts again when I replace the headers.

[san]

I cannot imagine another ebay set will fit any better. They're all shitty. My worry is that the threads in the head were already stripped enough to pull the studs out when you attached the catback section.

Ugh this is a tough spot. Can you try disconnecting the catback section, then re-snugging the nuts on the head flange? I'm really worried that they're toast, but it's worth a shot.

If you can do that and fire it up without leaks, then maybe you could cut through the piping in the catback section (like 6in after the flanges) and drive it to an exhaust shop like that and have them massage the pipes back to fitting.

That's really my only guess at this point. I'm super worried about the head.



I (of course) have a set of those headers in the garage! I bought them on sale and it came out to about $320 shipped. Really excited to mount them up and should be able to mate them to the rest of the exhaust by changing the flanges out for these: https://www.amazon.com/dp/B0015KZL1M/

I was hot on their full system, but you have to do a lot of cutting/welding to make it work with the 6 speed and people still had a ton of fitment issues. Great reviews for the headers themselves, though.

So will you be running without cats?


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[ZHPizza]

So will you be running without cats?


Sent from my iPad using TapatalkNah I picked up a 2in/2out cat to add downstream in a borla catback. I have two spun cats downstream of ebay headers on stock exhaust right now, but I think they're oversized for N/A.

[san]

Nah I picked up a 2in/2out cat to add downstream in a borla catback. I have two spun cats downstream of ebay headers on stock exhaust right now, but I think they're oversized for N/A.

What is the 2in/2out cat you speak of?


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[ZHPizza]

What is the 2in/2out cat you speak of?


Sent from my iPad using TapatalkThis one

https://www.magnaflow.com/products/94008-catalytic-converter-magnaflow-standard-grade-federal-epa-compliant-universal-catalytic-converter

[ZHPizza]

I think my block has probably has had enough torqueing of these headers, I think I'm going to undo these, throw them out, and get a better set. I'm going to assume the threads in the block are okay still, no sense assuming the worst for now. I will get all new studs and nuts again when I replace the headers.I keep thinking about this and if you haven't pulled them off yet, I'd suggest you run it again and try to confirm where the leak is. If it's from all-over the head connection then you have some serious issues. If it's just one or two spots then you may be able to snug those nuts down some more. Worth trying, especially if you can do it with the rest of the exhaust loose.


@san I was just bolting my exhaust back up and got some pics. I'll probably have to put the 2in/2out cat where the 1st muffler is, behind the transmission.

https://uploads.tapatalk-cdn.com/20201028/7b395e1ff3eff0345a4c756333fd3ad0.jpghttps://uploads.tapatalk-cdn.com/20201028/07da9c797063df9bf03d004a7a075895.jpg

[san]

I keep thinking about this and if you haven't pulled them off yet, I'd suggest you run it again and try to confirm where the leak is. If it's from all-over the head connection then you have some serious issues. If it's just one or two spots then you may be able to snug those nuts down some more. Worth trying, especially if you can do it with the rest of the exhaust loose.


@san I was just bolting my exhaust back up and got some pics. I'll probably have to put the 2in/2out cat where the 1st muffler is, behind the transmission.

https://uploads.tapatalk-cdn.com/20201028/7b395e1ff3eff0345a4c756333fd3ad0.jpghttps://uploads.tapatalk-cdn.com/20201028/07da9c797063df9bf03d004a7a075895.jpg

Appreciate the pics.

Every now and again I think of swapping the stock exhaust manifolds with some that are less restrictive but not without cats. So I’m quite intrigued by your project.


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