TIG welding cast aluminum

[ALLstrokedOUT]

Hello everyone,

My question is what the title says...Ive taken a used edelbrock intake manifold and drilled holes out to tig in some injector bungs. My friend and i tried to tig them in yesterday with no luck. I brushed the surface of both the intake and injector bung well with a stainless steel wire brush, but we couldnt get the filler to bond to the casting. Are there any tips or tricks to this? For a bit i tried preheating it with a torch, but didnt know what temperature i got it up to (or what it was supposed to be up to, 300deg?). Should i grind a bit of the surface of the casting down to get below the aluminum pores that have been exposed to the atmosphere?

Even though it is a used intake it is very clean with no carbon deposits or any obvious contamination. We were using a Miller Dialarc HF (i think 40-165amps?) with i believe a 1/8 green tungsten, but we also tried a smaller red as well. For the filler rods we also tried a couple different ones, i dont recall the number on them though...



Thanks for the help, this is the only thing holding my project up and would like to have this done privately and not pay for a shop (more for pride than monetary reasons haha).