Does anyone use a gasket sealer when fixing exhaust to heads, and if so what type?

Exhaust place I got custom exhaust made used a silicon based gasket glue which is a bloody pain to clean off and was used to stop leaks. I am now trying to fix some of their poor quality and want to get it right.

Also have had to redrill and tap head since they stripped the thread in one hole.

I used a product from SuperCheap.

http://www.supercheapauto.com.au/online-store/products/Permatex-Muffler-Tailp...

I bought some copper exhaust gaskets from somewhere, they are reusable after softening

Silastic.
No gaskets.
Permatex blue/red/grey/black, bathroom silastic, whatever.

3mm bead, put the pipes and nuts on but leave a small 1mm gap, don't tighten it up. Come in tomorrow and tension it up.

I have just beaded it up then re-fitted exhaust to pipes off the engine and driven off. I would drop the exhaust at the flanges every meet, then when I was done for the day, bolt it up with silastic on the flanges and just drive off.
Doing it this way it has never leaked, but hey, it's only been 20-30 years so there is still time!

Thanks guys. Was hoping for a short cut but the old addage still stands. There are no shortcuts.

Nothing but a good quality, thick gasket is required. Why? Well you'd be surprised how much pull in from the welding process happens to the 6mm thick exhaust flange. Run a straight edge across the flanges face and I bet you the bolt holes kick out leaving a 0.5-1mm gap at the centre of the flange where the exhaust pipe is.

If the flange is less than 6mm thick then over time the heat will naturally cause the flange to go concave.

So I always check the exhaust, inlet, heat riser and carb mounting flanges to be nice and level and if not I carefully file them flat

By doing this I have never had to use anything but the normal gaskets, well aside from never using those metal gaskets on the inlet manifolds but I digress

Well ended up using a muffler putty, and the car have never sounded so good. For the first time since getting the custom exhaust she has not backfired once since redoing some of his work. Still need to clean up the welds but mauy skip that till I boost the power more.

NO short cuts always flie the flanges flat by hand and use new gaskets

Well all seems good now. Almost no backfiring. Had a small one yesterday but assume it is due to the poor welding done by the exhaust fitter! Other than that it sounds better than ever!