Hi all some of you will remember I had a cat issue recently (another) I wanted a decat pipe and then to put cheap cats on a straight part but couldn’t see anyone that made one for the 4.2 so I ended up just buying one aftermarket cat. Looked the right shape etc but when we mates the trumpet of the cat to the trumpet of the manifold it’s a little twisted and diagonally there is a 1mm gap in one place it drive fine no light but you do get fumes occasionally at idle with the window open, is there a decent kind of gasket which would seal this by compressing in some areas and not others? Cheers Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

Dan, If it's just a 1mm gap then exhaust assembly paste will seal that, just put a good amount on the joint, do it up tight and start the engine straight away, it expands when it gets hot and seals the hole...

They do make lots of different gaskets, if the above doesn't work drop into an exhaust place and ask them if they have one to fit, should be cheap enough...  Pete

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2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

Any gasket will be of uniform thickness, it would need to be sufficiently soft to heavily deform on one side and merely compress on the other - I don't know of a material that can do that. If it were me, I'd take it off again and TIG a 'wedge' shim in place so that a gasket or ceramic paste will form a seal when refitted. Sounds a PITA job but you'd only need to do it once.

Graphite gasket will be the best, and, as hayland says whack a load of exhaust sealant on it,

Can you not use a 'Copper crush gasket' ? Used to use them on motorbike exhausts. Some of them have an asbestos core.