TIG/GTA with straight Argon shield gas is the top welding method for Al alloy, particularly cast.
Oxy welding thin section cast alloy tends to be pretty dicey, as the metal will liquefy very suddenly, and fall away in blobs if there isn't a backup plate supporting it.
Cheers,
Gadge
"ODK Mods can explain it to you, but they can't understand it for you..."
"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."
| 
