Hmmm, not the special hi-temp locking ones – STD-2043.
I am N-reg; paperwork is not a concern.
The engine that started this thread though is an O-360, these use STD1410 nuts on the exhaust which cost 20p each. According to the Lycoming parts catalogue you can use the STD1410 on the IO-540 as well. One thing I’ve never seen ever try to back off is an exhaust nut so I’ll stick with the 20p ones myself rather than have to contort myself into funny angles to do maintenance jobs that are far easier to do with the exhaust taken off!
On continentals, it is recommended to retorque after a few hours post exhaust gasket replacement. I have had them back off.
That’s probably not the nuts backing off though, it’s probably because most of the take-up of the torque was just overcoming friction when the nuts were first put on. If you mark the nut and stud you’ll probably find it hasn’t moved.
That is why one uses locknuts, and for some reason the high temperature ones are expensive.
Exhaust leaking is potentially a real problem.
There are three types of exhaust stud nuts in common usage the cheap ones from LAS, the standard ones from Lycoming and the self locking type from Lycoming.
The LAS type are OK if access is not a problem.
The standard Lycoming nuts are usually the most economic as these are slightly smaller than the LAS nuts and if the space is confined they are less trouble to fit and the extra cost of the nut ( over the LAS nut ) is offset by the Labour costs of fitting.
The Lycoming self locking type I have only seen fitted in locations that are tight and probably preclude the fitting of lock washers.
I would recommend all Exhaust nuts/ washers / lock washers are changed at each annual check. This is because if used for more than a year corrosion sets in and they can become corroded to the stud and this will require stud replacement. He cost of stud replacement can be many times the cost of renewing the nuts & washers at annually.
