Velvet951

How important are those special self-locking nuts that go on all the turbo exhaust? Can I replace them with normal bolts? The dealerships want like $6 a nut!!! Any suggestions??

David Floyd

I used copper nuts from Paragon

evil 944t

copper nuts from napa

Redshift

isn't copper a weaker metal? how well do they hold up?

Oddjob

I ran into the same thing with the $6 nuts.

So Ive used Stainless nuts with lock washers. I do have some concern about them loosening, because the lock washers lose their spring temper when heated in the exhaust system. But so far I have not had problems with the exh manifolds to crossover pipe flange or muffler/cat pipe flange.

I also just used them on the waste gate flanges and on the turbo exhaust housing. But recently enough (around 500 miles ago) that I dont know if they will loosen over time in these locations.

Most types of SS have a slightly lower thermal expansion than even high carbon steels. So a SS nut may actually "grip" on a carbon steel bolt/stud when heated. However, then the inverse may also be true (a Carb-Steel nut may loosen on a SS bolt/stud when heated).

Any metalurgists out there?

Velvet951

Do the nut and bolt have to be the same material? Will stainless for both work? Gottta get these today, so any other insight is most helpful!

Oddjob

I was kind of hoping some material science engineer would chime in with a difinitive answer....

I dont think there is a problem with mixing SS and carbon steel in these applications. Ive done it before.

SS metric fasteners are not easy to find. All I used to be able to get was the nuts and washers, so I used them with regular grade 8 bolts.

However, I did find a hardware store recently that has a pretty good selection of SS metric bolts, so I used those when putting together the exhaust system about a month ago.

The SS will probably not have the same hardness rating that the carbon steel bolts have, like 8.8, 10.9, etc. So depending on the application and bolt size, you may want to be carefull with torque specs. But I dont think there is any strength problem with exhaust components (suspension bolts may be a concern).

The other thing you will find is the head size for a given bolt diameter. Many of the exhaust bolts/nuts on the car are M10 with a 15mm head. Standard head size for an M10 is 17mm. The larger head will cause some clearance problems on the flange surface. So if you replace the 15mm heads with 17mm, just make sure the wrench/socket will fit over the bolt head without interference from the flange, before getting too far into putting it all back together. M8s are all the same size so no problem there.

alengyel

John, the Fastener Center should have what you are looking for if you have the time to go by there. There is another place and I think its called something like Fastener Engineering on 17th south just east of 300 west that should also have it. The copper nuts on my exhaust manifold have held up better than the stainless studs and don't seem to weld themselves together like SS or Carbon Steel. Given the fact you run a K27, you may not need the low profile nuts that the K26 require. Hope this helps and thanks again.

Ahmet

I thought copper was used so that the nuts wouldn't bond to the steel... I've used standard copper locking exhaust nuts also, no problems so far.
Ahmet

Hans

Am no metallurg (??), but have been doing this for a lot of years at previous cars:
For head to headers:
Studs remain steel, then stainles nuts class A2 with lock washers.
Studs stainless, then brass coated locking nuts (from VW).
Anything further down the line does not realy heat up that much so it doesnt matter, you can even use stainless bolts and nuts without seizing them.
Just torque them as if 8.8 grade steel exhaust bolts (by hand, stop pulling about 180 deg befor they snap off)
Just practical experience, no science here.
TakeCare