Exhaust manifold studs/bolts

[rubjonny]

shouldnt do, after all thats what vw will sell you if you go buy some today.
ive had a set on another car i built since 2007, still look just as good as when i fitted, if a bit tarnished

[AudiA8Quattro]

Its also what vw will sell for exhaust nuts, doesn't mean they will last.
Copper is soft and will crumble.
Each to their own, i'd prefer stainless steel any day.

[emery1990]

coppers not cheese lol, uses it everyday is a soft metal, but a solid nut will not crumble unless you leave acid for ages!, lasts in houses for years and years and years and years.

[jezza16v]

Nuts? I need the studs as well. Surely the nuts wouldn't be pure copper as you wouldn't get any torque on them before stripping the threads? Probably some sort of alloy closer to brass to make them harder. I know stainless steel is a bit less predictable than normal steel, but again S/S is an alloy, I presume the S/S studs nuts would be of an alloy mix to suit their use rather than 18/8 you get for a kitchen sink which is quite soft. I note GSF list 8mm copper nuts which I presume are for the exhaust manifold but they don't appear to list the studs? I know you chaps like a pic, here's the missing stud on No1, you can see that the gasket has been fitted on the slant so I guess that wouldn't do much for the gas flow, mind you probably burned away?

[Diamond Hell]

VW are bloody cr@p with their exhaust studs and nuts - specifying poxy M8 studs and nuts - it makes them extremely prone to wasteing away over time, so 12mm nuts become 11.5mm nuts and the exposed steel threads crumble away..... that said you lot have got it easy vs Waterboxer studs and exhausts on T25 Transporters 

I'd be inclined to put some meas or loctite on the thread going into the head.

No, it'll burn off and the nuts will come loose.

Will copper not go soft and break up?

No, it'll waste very similarly to the steel studs.

I would of thought stainless steel would be better as the fixings won't seize, so won't snap.

They'll shear very easily instead.  Stainless steel fixings are generally a lot softer and this isn't the right situation to use them.  Show me the tensile rating on the stainless fixings.  The peened copper nuts with the 8.8 studs are essential in this application to keep the manifold up tight. 

You should use the correct VAG spec plain washers, too as standard plain ones are generally shyte quality and considerably thinner than the VAG ones.

[X4MGS]

Correct me if I'm wrong but don't SS not react to heat as well as the OEM ones?

I have read in the S2 forum about peeps using SS malifolds and having nothing but problems with them when fitted to "Everyday" Cars... For track or Race cars fine...

Just me 2p's worth...

For Me OEM everyday all day... when you consider we are still running cars over 20 years old, with a build quality second to none these days... How many astra's, Rovers will be around in another 15 years??? VW get most stuff right...

[mwep201081]

I'd be inclined to put some meas or loctite on the thread going into the head.

No, it'll burn off and the nuts will come loose.

No it won't.....meas goes hard with heat.....I sat through an 8 hour meas and loctite seminar last year, and all our exhaust and turbo studs at work have a meas patch on them....

I did say on the thread going into the head too....not on the section where the nut will be.....

[myvr6isarocket]

Tensile strength and Young’s modulus for selected materials
material   tensile strength MPa   modulus of elasticity GPa
304 stainless steel   500                                       200
copper                   270                                       120

Stainless steel has a higher tensile strength than copper,
Tensile strength... the ability to withstand a pulling stress,
Youngs modulus of elasticity...the ability for a material to withstand plastic deformation and return to original shape and size with negligible change in dimension
There are many different grades of steel and to say "steel counterparts" without being more specific is pointless imo?

[AudiA8Quattro]

They'll shear very easily instead.  Stainless steel fixings are generally a lot softer and this isn't the right situation to use them.

Fair point.
I haven't replaced manifold studs, so only stating an opinion. However for general exhaust fixings, i have found stainless to be more useful in the longer term.

[jezza16v]

Tensile strength and Young’s modulus for selected materials
material   tensile strength MPa   modulus of elasticity GPa
304 stainless steel   500                                       200
copper                   270                                       120

Stainless steel has a higher tensile strength than copper,
Tensile strength... the ability to withstand a pulling stress,
Youngs modulus of elasticity...the ability for a material to withstand plastic deformation and return to original shape and size with negligible change in dimension
There are many different grades of steel and to say "steel counterparts" without being more specific is pointless imo?

So what are the figures for the normal steel studs, I reckon they would be GR 8.8 circa 555/205. I presume those figures are at 20 deg C but what would they be at exhaust manifold temperatures? Mild steel and high tensile steel MPa values drop off significantly above 300 deg C, I guess copper would drop of much earlier.

This thread is getting a bit boring now isn't it..........sorry.