Permatex 81878 3 Oz Ultra Copper RTV Silicone Gasket Maker (2 Pack)

This is superb for sealing exhaust manifolds, I have used this when I could not get the original gasket, worked first time, saved me hours! I cant recommend this enough!

Shows 2 tubes in the picture. Description says 2 pack. Costs about what you'd expect for two tubes, but you only get one. Just go down to the local auto parts store.

Worked great on old Harley Davidson exhaust gasket

One of my go to gasket makers. Works great on uneven surfaces.

I used this to seal the gap between the top and body of a 26" Weber so I could control the temperature. I coated the kettle with Vaseline to keep it from sticking, then put a heavy bead around the top and left it on the kettle to harden. It took about 2 days, but now is excellent. If you do this, make some kind of mark on the top and kettle so you can easily align them later. Otherwise the top won't go on tightly. It took almost a full tube.

Product works fine for exhaust work. The cheap tube split in my hands and got gasket maker everywhere though.