I posted pics for another discussion, so might as well spread some weirdness here too. I didn't have access to a TIG welder at the time, or funds to pay someone.
I actually JB welded an aluminum cyl head on my Datsun truck. It corroded as the PO had never changed the coolant, and it undermined the metal ring under the headgasket, allowing the gasket to blow. The hole didn't actually enter the combustion chamber. I figured i would junk the truck rather than buy a head, so i used a spot-blaster to clean the metal, epoxied it and filed it smooth. It's been 4.5 years and still holding. I wouldn't have believed it, and would never have tried it on someone else's engine.