fitting my mondo muffler part 2: getting a good seal?

[baron]

so i replaced my leaking twin quiet pack fr a shiny new mondo muffler the other day

first impressions were great, it seemed to give a little more power which suprised me, but maybe the old twins had been leaking fot a while, but after a while i developed a backfire, and investigation revealed a leak from the seal with the header flange

i'm using a copper gasket, which i guessed would be tricky to seal, but i did give the flange a light file beforehand to give a good flat surface to seal against

any more suggestions to help get a good seal, other than applying a bit more strengtt to tightening the bolts

 

[ProfessorWheeto]

Exhaust gasket sealing paste available from your local motor factors. Comes in a toothpaste tube or in a tube that you'd fit to a mastic gun.