Latest 403 issue

[Geoff Kingston]

In Racing can supply the original exhaust system manifold nut which is how they describe the sleeve you refer to, I have seen a few of these damaged over the years and also manifolds where brute force has failed to achieve what the perpetrator set out to do.
More common I found was deterioration of the threads on the manifold itself either through rust or burnt away because things had become a bad fit.
If you are able to try the nut from the back pipe on the front manifold ( I am assuming they are a good fit) that should determine which component needs replacing, I don't know if the end of the manifold could be built up and the thread re cut and even if it could be done if it would be a cost effective option but out of interest I will ask my friend Brian who is a very clever engineer and welder and see what ideas he comes up with.
Second hand might be an option from a reliable source but it is worth remembering that when new these components were hand lapped together to give a good seal without any exhaust sealants so if you can, try and get a pair that are fitting and tightening up properly.
Another option I have seen on a few cars is where new manifolds and down pipes have been fabricated, often in stainless steel, which have done away with the original type of manifold/front pipe joint completely.
Geoff.