Exhaust Stud Came Off, How To Fix Aluminium...

Anything to keep us riding cheaply!
Worst that can happen is it lets go and you get some extra exhaust tone

 

+1
The only way to repair this is to weld repair it.

In theory there should be another 10mm of aluminium behind where the drilling ends, so you could try drilling and tapping deeper. Right now its scrap so you can't make it any worse.

If you can get the head to me, I can weld, re drill and tap it for you. But the head will need to be stripped because we have to pre heat aluminium prior to welding.

Either that or it's a replacement head from a breakers.

 

You don't have enough threads left to try this, you would need to drill deeper and tap deeper.

Ideally you need at least 1.5 × the thread diameter deep, so an 8mm stud should be in 12mm. At the very least you want 8mm of thread depth.

 

if you are not going to remove the head why not try and use the Kwiksteel epoxy putty. just force into the hole and build it up to how it was before. then drill & tap it. if it doesn't work you have lost nothing other than time. if it does work you have a result.
I have used the stuff on few jobs and found it very effective.

 

Any chemical metal will crack due to differing expansion and contraction the only way is to weld and re drill/tap.

 

That section has torn clean off, if you look closely at the break you can see how crystalline the metal is, I'd challenge the material they cast it out of in the first place.

I've no idea where triumph source their parts, but the stuff we see coming out of China can range from laughable to downright dangerous.

If a supplier can use something cheaper and they think they can get away with it, they will.

 

Not necessarily so....

Back in the 90s I tig welded a number of Ali heads for a friend's business. They ranged across multiple brands. BMW was definitely by far the worst, I think they'd melted old saucepans or something. Nissan in comparison was excellent clean material of a far superior melt.

As I mentioned previously chemical metal is not appropriate for this repair.

 

Not exactly sure which bit of my post your challenging, and all challenges are welcome, but I couldn't agree more regards your statement that quality is brand specific. And the Japanese are still regarded the best for quality, certainly in tooling, which is what I do.

A previous employer did work for Triumph a number of years ago, but the parts were cast in India, that didn't end well either.

 

Arudge I agree on the crystalline appearance as I commented on this in one of my earlier posts but.... assuming its the original, the casting is at least 22 years old so hardly a poor casting from dubious material: don't you agree?

I'm not sure the country of origin is totally the answer either as rubbish (and good stuff) is made all over.

The actual fitting of the current and/or previous exhaust studs plus possible previous over tightening of the exhaust manifolds to resolve leaks rather than fitting new gaskets etc. stressing an area subject to expansion and contraction is never a good combination.

 

Hello Eldon.
It's not the quality of the casting itself, but the material they cast.

The bit that bothering me is that the boss was large enough to take the load, and the threads should have failed first, yet the whole front came away.
And the OP was told this has been seen before.

I havn't worked with gravity castings since the 90's, when most heads and blocks were cast from LM11. I've sawn countless casings up to check section thickness and sand core locations, the material never had a granular appearance like that. That's why I'm wondering if the original casting material was up to spec.

I'm sorry for sounding so sceptical but I make my living repairing stuff that should never have failed, but more often than not the failure occurred because somebody tried to cheat/save money/use inferior materials. You've go to see it to believe it!! The worst culprits are India and China, but their so cheap!!

I know some of triumphs castings came from India because an ex employer was the supplier, but I don't know what they supplied nor when.

 

Yes fair comments Arudge and i think we agree on most of the technical points.
I'm also of a cynical and sceptical nature so for something to last 22 years then fail something has changed.

OP, did the old studs come out easily or were they seized?

Has an anti clockwise strain initiated a fracture within the casting so that when compounded with a clockwise strain the casting failed.

 

The old expression in the trade was "boomerang heads" as in so many were warranty failures.

 

A very valid point, but given that everything looks so clean, the stud clearly hadn't bottomed out and 'jacked the front off' I'd simply say the OP overtightened it, and torque wrenches are so very unreliable. I have three calibrated wrenches as none of them can be trusted from one end of the range to the other.

And neither do I wish to criticise the OP, but it would be interesting to know if the OP felt he may have overtightened the nut regardless of what the torque wrench was telling him. Even so, the casting shouldn't have failed like that, we've all pulled threads out of alu castings, that's what helicoil inserts are for

 

original poster

 

That’s an interesting collection of bikes. Liking the Falco cafe racer. Hope you had a great trip.