I've burnt through my 2nd exaust manifold gasket in about 200 miles. This is the gasket between the head and the extractors. Centre exhaust port burnt through - Maniflow extractors on a 1275, standard size ports.

Last gasket change i did all the right things:
cleaned all the faces on extractors and head
made sure everything was flat (cleaned up with a flat file)
new standard type gasket (grey with metal insert) installed dry
ensured everything was seated properly when doing up.
retighted nuts after warming up
retighted nuts after a drive

Looking for ideas, what are others doing with success?
VHT Copper coat?, smear of hi-temp silastic? anything else?

Novelty of doing gasket changes is wearing off.

Diecast

did you measure the thickness of the manifold flange on the extractors against the inlet manifold flange and make sure the washers were thicknessed accordingly?

I had that trouble and I think I ended up getting the extractors ground flat and the same thickness top & bottom

1. Maniflow LCBs- the middle flange is not flat, or in the same plane as the end ones. Usually. Cure- grind/file it flat.
I bolt it to an old head with no gasket, then check around with a .002" feeler gauge.
2. There are better manifold gaskets- Unipart do a turbo one with metal rings on the exhaust ports. See Mini King or Karcraft.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

every thing looked ok as it went back together, inlet manifold and extractor flanges same thickness etc

metal ringed gasket sounds good. Installed dry? or with any type of goop/copper coat/loctite etc.

Thanks for the help guys

Might seem un-related but is your ignition timing right?

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Ignition is ok, starts easy, no pinging, runs strong to 6500, fuel mixture, engine temperatures good, RC40 exhaust etc. If i was having issues here, then yes ignition timing might be an issue. Seems to me to just a direct mechanical issue

Both gasket problems have occurred at the end of track days. 1st Gasket failed after 3 track days, 2nd gasket failed after 3x sessions at a track day.

Just looked online and seen a picture of the turbo exhaust gasket, looks like it will do the job, thanks doc

I'd get out the verniers and measure all the flanges. A few mm either way will stuff things up. Make sure you use the proper thick exhaust manifold washers and new nuts (don't cost very much from minis.com.au, in fact I think they sell a whole set).

Manifold gasket mounted dry. I've never had problems with std gasket when done properly...

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Lillee - 1969 Morris Mini K