Originally Posted by .redshift
Agreed. I am picking up some of that copper RTV tonight. I scraped the flanges with a razor blade until they were smooth as a machined face, but no dice. Haven't had them apart again to check straightness, but I think they may be warped.
Doubt they are warped, just a nice layer or rust. It will look smooth, but I promise it's rusted and needs to be smoothed down. Buy a sanding disk for a drill from home depot if you want, but the rtv should help. Lay a bead then spread it with your finger.