Latest 403 issue

[peterg]

The exhaust pipe sleeve no longer screws securely onto the front manifold. Am I likely to need to replace both parts, or were they designed so that one component would fail first? Following up on this, is it safe to replace them eith second hand parts?

[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.

[dave dale]

A few years ago I had the same problem with my 403. As Geoff K correctly observes, the threads in the manifolds were corroded and allowed the bronze nuts ( correctly called ' peg nuts ' with reference to the tool that is used to tighten them ) to slip over the threads when an attempt was made to tighten them. Spencer Lane - Jones had supplies of replacement nuts in stainless steel and in three slightly dissimilar sizes of thread, to accommodate varying degrees of manifold thread wear. If one of the three sizes is a close fit, the nut can hopefully be tightened up without too much force or used as a die to cut it's own thread into the manifold by reshaping the faulty existing thread, thus obviating the need to subject the manifold to a proper re-thread. At least, that is how I understood it at the time and it worked for me. You could try Peter Campbell ( fount of all knowledge and the head of S L-J ) office@spencer-lj.com Telephone: 01985 847133. Hope this helps.
Dave Dale.

[peterg]

If only that was so Dave, but it is the exhaust nut that is slipping over the threads on the manifold. The brass nuts are all good