Head to header gaskets?

The factory did not use any gasket to seal the headers at the heads. Also, the stock bolts are used with a captured lock washer so it will not loosen. Stock flanges do warp, especially after 25 years of use, and a leak is probable.

I have re-installed too many leaking stock headers, so my customers now always get gaskets, as I want to do the install only once. ;)

If you are going to use an aftermarket set of headers, it may leak w/o a gasket?

Some aftermarket headers use a much thicker flange, and it will NOT comply very well, if at all, to the head surface, so a leak is probable.

On alum heads where you do not want to apply as much torque as you would with an iron head, gaskets are recommended as well a bolt or stud that will not loosen.

What we have found that works best for us is to use copper gaskets, coated both sides with hi-temp silicon, and the use of studs with flanged nuts. My copper gaskets have been re-used at least 6 times, and are still working good! :)
Thanks nick.... I knew GM didn't use any.... any certain brand on the gaskets or the silicon?
I bought a set of SCE copper gaskets and have been using them ever since and that was 13 years ago. One of the best purchases i made even though i thought it was a little expensive for gaskets at that time. I also bought the copper turbo to header mount gasket and the turbo to down pipe exhaust gasket.