Stripped thread on exhaust stub

[John Roberts]

Mr. Ron and Steve:

Now this is interesting. I had assumed that the stub around the knackered thread would be built up by welding and then re-machined with a new thread. It isn't because I'd been told or that I'd worked it out- I just took it that that was the way to do it. I'm not that familiar with welding alloy, but I suppose it could be done like that.

Hence my interest in hearing how the job is actually being done. Yes, Steve, it would seem that the new tubular insert would have to be keyed into the head in one way or another or it would sooner or later work itself loose- just think of the initial force - the grunt- (good word, that!) you need to undo the finned nut. Hmmm... perhaps a Left Hand thread would be better where the sleeve screws into the head so that it would further tighten in the head (rather than unscrewing) when you tried undoing the finned nut. Oh, then on the other hand there would be a tendency for it to UNscrew when you tried tightening the finned nut. Swings & roundabouts. You are probably right there, Steve, it would have to be keyed (or pegged) to be reliable. I still think that threading would be an added bonus compared to a shrink fit, though, but if that's the way it's done then it must be good enough.

Thanks again,

J