[eschaider]

Bill hit the nail squarely on the head. Your flanges are warped!

Mill them just enough to get them flat or replace them. Everything else is just going to prolong the pain and suffering. Of course, if you are into pain and suffering, that might be the preferred path to follow ...

BTW, if you don’t properly fix them, it is still possible to enjoy continued pain and suffering. All you need to do is mill them too thin, and you will be good to go for another round of pain and suffering.

Then of course, you could just go and buy a nice set of 3/8ths or half-inch (if you are a bad welder) flanges, put them on, and forget about all this crazy gasket stuff — but that wouldn’t be much fun now, would it? Moreover, what would you have to post about?