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MG MGB Technical - TT exhaust clearance

I have 1969 mgb roadster, owned for 23 years The two box stainless steel exhaust, whilst still serviceable has gradually been developing an annoying resonance due to the box packing disintegrating over recent years. It fitted well with good mountings and no rattles, just a rather wearing harmonic.
Anyway, I took advantage of a.Moss offer and bought a Tourist Trophy three part, single rear box system that uses the original cast iron manifold.
My problem is is this. When fitting up the new Y front pipe solid flange to the original cast manifold flange, the back end of the TT front pipe butts up against the gearbox cross member and wont allow a flush fit and hence the new gasket will leak. Theres an approximate 3-5 mm gap between the two flange faces (v hard to measure exactly from below or above).
This was not a problem at all with the old front pipe that used the twin OE sealing ring fixing.
I went to see Moss with my new front pipe and they compared my TT one with another one straight off the shelf - they were identical. They were very helpful but I left after a long chat with no solution. Im aware the TT system has a very good reputation.
Thinking about it all, it would seem that the front of the engine might be sitting slightly lower than it should be hence the angle of the manifold face is such that the TT Y piece face is incorrectly aligned and pushes up the rear pipe after the join up onto the gearbox cross member. The rectangular engine mounts are clean, not cracked or soft and bulging. The rear gearbox mountings are as they should be and in similar condition.
Any suggestions as to where to go next with tackling this would be welcomed, thanks.
r hamlyn

If the front of the engine were sitting lower then it would pivot around the gearbox crossmember. So the exhaust at that point is likely to be in more or less the same place and it would be further back that the pipe would be angled up.

It doesn't surprise me that two TT pipes were the same, it would be more interesting to compare your original pipe with a TT and other offerings they have.

From what I've 'heard' the TT can give a loud and annoying drone at cruising speeds. I've had a 2-box stainless system for around 30 years and initially it was disappointing - rather 'farty' instead of the very distinctive MGB mild-steel sound. But since partially crushing the centre box over rough ground many years ago it sounds much nicer!
paulh4

Paul, thanks for your response.
We did indeed compare the old against the TT front pipe before visiting Moss in Feltham. As the two systems have different fixings to the iron manifold flange it’s hard to be exact but the top mating surface of the collars on the old seems to be about 5mm + higher than the top surface of the flange on the TT front pipe. It was this that prompted the visit to compare TT pipes in case mine was a one off.
Regarding the noise factor it does seem one rather takes pot luck in choosing a replacement system but I had experienced a TT system on a friends B and it seemed reasonable.
Either way, at present I’m caught up with a couple of other projects so will refit the old system in the next day or so so the car is useable again.
I’ll ponder further on what to do about the TT system and continue to take further advice from anyone with possible solutions. Thanks again Cheers Richard
r hamlyn

Sounds like the TT verticals are too short. If they were flat flanges you might be able to fit a spacer.
paulh4

This thread was discussed between 19/06/2023 and 21/06/2023

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