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Discussion Starter #1
So I started hearing what sounded like a bad exhaust leak coming from the engine compartment last night. I checked the tightness of the exhaust manifold nuts and discovered that the previous owner or mechanic had stripped the stud closest to the firewall (lower exhaust manifold stud). The nut spins almost freely by hand while the stud is stationary, so I'm assuming the stud is stripped. Ugh. Snugging the other nuts helped slightly with the exhaust leak noise, but I noticed also that I had some exhaust/smoke coming from the area of the rear "V" on the manifold.

Observations:

-I don't see a crack there when I shine my light on the "V" area, but maybe these things don't make themselves obvious. See the attached pic for the location where the exhaust is coming from.

-I noticed a little oily grime around the edges where the manifold meets the head for the port that had the stripped stud.

-Looks like the p.o. installed an aftermarket exhaust setup, fwiw.

Questions:

-How much of a nightmare is it to replace the stripped stud? Is it even possible to replace, or it a cast part of the head?

-If the exhaust leak is mostly coming from a cracked manifold, do you think i can get away with leaving the stripped stud in there for now, since the 2nd nut on that port can be tightened without trouble?

I just had to pull the head off of one of my BMW's and I'm really not in the mood to get into another huge job like that on the Alfa. :( :( Any feedback or advice is greatly appreciated!!!

-Adam
 

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with a bit of luck it might just be the nut that has stripped (IF the PO used the correct brass nuts, that is!)...brass is softer than the hardened steel stud.
You'll need to remove the nut to inspect it and the stud.

Yes, it is a stud, so can be backed out if it is indeed stripped....but manifold will need to come off to get any purchase on it with a pipe wrench or similar (plenty of threads on the BB about this)

Alfa used brass nuts there for a good reason!
 

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Discussion Starter #3
with a bit of luck it might just be the nut that has stripped (IF the PO used the correct brass nuts, that is!)...brass is softer than the hardened steel stud.
You'll need to remove the nut to inspect it and the stud.

Yes, it is a stud, so can be backed out if it is indeed stripped....but manifold will need to come off to get any purchase on it with a pipe wrench or similar (plenty of threads on the BB about this)

Alfa used brass nuts there for a good reason!
Thanks for the reply. I can't get the nut to back off the stud. When I unscrew it it basically just sits in the same place. I'm PRAYING it is just the nut stripped… That would be a most welcome issue! Any tips for backing it off of there? Only thing I can think of right now is to loosen all of the manifold nuts so I can put pressure on the back side of it… ?
 

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You might be able to fit a small nut splitter on there to break off the nut, then check out the threads on the stud. Maybe pick up some studs ahead of time in case you need to replace that stud.
 

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Agree with what others said about the stud.

Unfortunately, that style of exhaust manifold does tend to crack, and when they do, it is often in the area where your red arrow points. The crack may be on the side facing the engine, so it isn't that visible.

Are you sure the manifold-to-downpipe seal is good? Perhaps the manifold isn't cracked and you just have a leaky gasket.
 

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Discussion Starter #6
Agree with what others said about the stud.

Unfortunately, that style of exhaust manifold does tend to crack, and when they do, it is often in the area where your red arrow points. The crack may be on the side facing the engine, so it isn't that visible.

Are you sure the manifold-to-downpipe seal is good? Perhaps the manifold isn't cracked and you just have a leaky gasket.
Actually I'm not sure that seal is good. I suppose I need to check that out, as well. It's possible the exhaust smoke I saw was coming from that connection.

John533i, I'm not sure I can fit a nut splitter in there. Looks like the manifold tube might not allow enough space. Any other ideas on how I could get it off?

One more question. Is the manifold I have look like the original type that would have come on the car? Just want to know what to order if mine is indeed, cracked. Is there a alternative, 'higher flow' manifold I could fit on there that would still fit with the down pipe I have?

Thanks again, everyone-
 

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RenaissanceMan said:
I can't get the nut to back off the stud. When I unscrew it it basically just sits in the same place.
I hate to be a pessimist, but from the symptoms I would bet that the stud is stripped. What typically happens is that the stud loses only the threads where the nut sits - while the threads at its outer end are still there. So when you turn the nut it doesn't back off, and you can't just yank it off because those threads at the stud end retain it.

You may need to apply force to the nut while turning it - can you get a screwdriver behind it to pry it back while turning?

Is there a alternative, 'higher flow' manifold I could fit on there that would still fit with the down pipe I have?
I don't think there is any aftermarket header that fits the 1986 style of downpipes.

The partial solution would be the earlier style, two-piece manifold. Less flow restriction, not as prone to cracking. But it won't bolt up to your existing downpipe - you would need to replace at least the front part of your existing exhaust system.

Does your '86 have a catalytic converter? If it does, and you need to retain it, some custom fabrication would be required to connect a cat to the early-style exhaust manifold. If you don't need a cat, then early-style exhaust components should fit your later car.

Here's a picture I found via Google of the early style manifold:

 

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What typically happens is that the stud loses only the threads where the nut sits - while the threads at its outer end are still there. [/IMG]
Jay is probably right. Just put another nut on top of the stripped nut and run it down. The stripped nut will act like a washer
 

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I would try your idea of loosening or removing all of the other manifold nuts and then use a piece of wood to pry between the head and the manifold while trying to back the offending nut off of the stud. Or, try flivsay's idea. I think it is 50/50 between the nut or the stud being damaged.

If you have a cracked manifold, it is not particularly expensive to find an early manifold and down pipe and pay you local muffler shop to weld the exhaust pipe to the new down pipe. The shop will also need to weld in a bung for the O2 sensor. I had a manifold and down pipe and paid the muffler shop $100 to do the fabrication work on the '88 Spider. After two years, no regrets.
 

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You are going to have to remove the exhaust header in any case. If it is cracked you will have to replace it. If not, you need to remove the suspect stud for inspection. If the stud has stripped out the threads of it's hole, you will need to install a helicoil to really repair the stripped out threads permanently. You can read up on helicoils and their installation on the net. I have installed many helicoils over the years in aluminum castings and they are simply amazing. Since you have to drill out the stripped hole to an oversize, you will be installing the helicoil into virgin material and if you install a helicoil correctly, it will hold forever.

Robert
 

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Discussion Starter #12
Update:

Well, I finally got the nut off. There was no way possible to get anything behind the nut to push (was completely flush against washer/manifold), so what I had to end up doing was loosen the rest of the exhaust manifold nuts so that the weight of the exhaust would pull against only the stubborn nut. This provided the force needed to back the nut off while I loosened with the ratchet. Was a piece of cake once I figured this out!

Now, when I took the nut off I got excited because it appeared only the nut threads were messed up… But, upon closer examination it looks as if the threads on the stud, itself are indeed flattened a bit in the middle where the nut was tightened. :( I've attached pics so you can see.

I didn't see any cracks in the manifold, so I'm going to assume that my exhaust leak was coming exclusively from the loose manifold nut, or… a combination of that and a leaky gasket connecting it do the down pipes.

So now the big question is, how in the world do you safely remove a stud from the head while it's in the car??? :) :) :) Do you think I should leave it in there and just use a couple of washers as shims to keep the nut on the good part of the threads, instead?
 

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Try a 8×1.0mm die it may restore the threads first. If not try to double nut to remove the stud.You can also purchase a stud removal socket for a 8mm size stud,just flag down a snap-on or mac tool truck.
 

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Run the correct die on the stud to see if it will clean up the threads. You can try to double nut or put 2 nuts on the stud which locks them together and try to turn the stud out with a wrench. Use the good threads
 

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Discussion Starter #16
Run the correct die on the stud to see if it will clean up the threads. You can try to double nut or put 2 nuts on the stud which locks them together and try to turn the stud out with a wrench. Use the good threads
Are these studs typically pretty easy to get out? I'm just a little apprehensive about needing to use enough force that I might risk damaging the threads in the head. Thx-
 

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It should come out. For peace of mind you can lightly heat up the surrounding aluminum with a propane torch.

Looks like regie185 posted the same info while I was typing--so 2 same opinions
 

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I like the stud removal tool idea. Maybe Harbor Freight has something? I've seen them in action; nifty. Removes stuck studs with otherwise good threads with out ruining the threads, also.

Like someone else mentioned, you can buy manifold studs with hex heads in them which makes removal much easier the next time. I bought mine at ACE Hardware- they are universal. Order some new nuts from IAP or Centerline, though whatever you do.

I Might even try spraying the stud with liquid wrench and using vice grips to see if I couldn't budge it that way...:001_unsure:
 

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you could re-thread it with the stud still on the engine (by removing the manifold) and get a matching nut..
 

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To re-iterate the good advice above, yes, the stud should come out without a lot of drama. Double nut on the good threads, locking the nuts against each other. Definitely apply some heat to the stud prior to loosening as it may have been installed with Loctite. BTW, the end of the stud that goes into the head has 8mm x 1.25mm threads (as opposed to 8 x 1mm on the manifold end).
 
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