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Right after I purchased my Spider, while changing the rusted out downpipe/cat section, I discovered that one of the exhaust manifold studs was missing. Since the missing stud came out of an M8x1.25 through hole, I just threw an M8 bolt in there when I installed the new downpipe.

I recently removed the downpipe to facilitate the removal of the gearbox and to change motor mounts, so I though I would take this opportunity to put in the proper M8x1.25 stud. When I began sourcing M8x1.25 manifold studs in a 40mm length, I found that they came in (at least) two different material grades, and I'd like to hear what the group thinks would be the best material for this high-heat application.

One type is a black "Alloy Steel":

M8 x 1 25mm x 40mm Alloy Steel Exhaust Manifold Studs Custom Quantity | eBay

The other grade is stainless steel:

M8 x 1 25mm x 40mm Stainless Steel Exhaust Manifold Studs Custom Quantity | eBay

I think someone on this BB once advised against using black studs in the head, but I'm wondering if that holds true for manifold use too. The stainless are slightly more in price, but that is not a concern. I just want to use the best (or proper) material.
 

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Studs

I think either would be ok. The "black" one has higher strength. I normally use stainless steel if I think I am going to ever remove the fastener again. I would replace all at the same time. My exhaust system is held together by SS bolts and nuts, no problem.
 

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I would not use generic studs. The length of the threaded section that screws into the head is important and so is the length of the shoulder in the middle. Using the wrong ones will result in stress points that could lead to fatigue failure. Call Larry at APE and buy good used studs from an Alfa Spider cylinder head. Also, use Loctite on the threads that screw into the block.
 

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I would not use generic studs. The length of the threaded section that screws into the head is important and so is the length of the shoulder in the middle. Using the wrong ones will result in stress points that could lead to fatigue failure. Call Larry at APE and buy good used studs from an Alfa Spider cylinder head. Also, use Loctite on the threads that screw into the block.
Hi Ed,
Just curious as to why you would recommend used studs over new ones from the popular Alfa suppliers. Is there a benefit also to using the brass nuts?
Cheers, James
 

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I am with Ed on the stud issue. It is quite important that the shoulder exists in the correct place and be the correct length. The part that threads into the head is 8 x 1.25. The external part is 8 x 1.00. Corrosion is not a problem if brass nuts are used and even less so if a little antiseize is applied. Stainless fasterners are suseptible to gualling in manifold (high temperature) applications. Others have posted problems with non-oem exhaust studs breaking, leaving part of the stud in the head. "New" is more and more frequently not "better".
 

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Ed is correct about the studs into the aluminum head. But you are talking about the exhaust system, different animal.
 

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Yes, the case of the manifold to down pipe is a different animal. I typically use a good steel alloy stud or bolt and plenty of anitseize. I would not use stainless in this application.
 

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Ed is correct about the studs into the aluminum head. But you are talking about the exhaust system, different animal.
My post was about studs into the head, sorry for the confusion. But it is important that the root of the thread of a stud is not aligned with the shear force where the two parts meet as that is the weakest part of the stud.
 

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My post was about studs into the head, sorry for the confusion. But it is important that the root of the thread of a stud is not aligned with the shear force where the two parts meet as that is the weakest part of the stud.
I don't mean to hijack this thread but, Rich, what would you recommend if you have to replace damaged exhaust studs, new studs or used "OEM" studs. I need to replace a few of mine?
 

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I would use a steel stud and not a stainless steel stud. I would also use a locking steel nut with antiseize compound which I use on both of my Milano cast iron exhaust manifolds. I use brass nuts on the engine exhaust manifolds for my two Milanos and my 101 Sprint Veloce.
 

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Locking steel nut?

I would use a steel stud and not a stainless steel stud. I would also use a locking steel nut with antiseize compound which I use on both of my Milano cast iron exhaust manifolds. I use brass nuts on the engine exhaust manifolds for my two Milanos and my 101 Sprint Veloce.
Hi Kuni,
Thanks for the advice, but can you please clarify what you mean by a "locking steel nut"?
Surely you are not referring to the "nylock" type locking nut (that has a nylon washer encased in the end of the nut). I'd be concerned that the nylon material would be affected by the heat and lose it's locking ability.
I was planning on using "split" type lock washers under the nuts on the anti-seize coated studs.
 

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You are right about not using the locknuts with nylon, they can not take the heat. Their are other types of lock nuts, but can be hard to find in metric. Use a heavy duty lock (split) washer. I think that is what the factory did.
 

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I am anal about replacing every possible fastener on my 88 Quad with stainless steel, EXCEPT the manifold and exhaust hardware. I use a high quality steel fastner and where heat is concerned I use the brass nuts which IAP sells for such applications. Also a steel split ring lock washer such as Richard so kindly pictured. Elastastop nuts will not work where heat is an issue.

Works for me.

Robert
 

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If you can not get the metal locking nuts Ed linked about above, use the split washer. Wave washer is more for spacing like behind the vent window handle.
 

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The wave type washers are for use against aluminum. Split washers are for use against steel.
 

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If your using brass nuts on the manifolds you use flat washers behind them.
 
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