FYI Justin at R^D has these with a 3" 45degree tube already welded on it. I think like $180 with your core. I sent him my filphy one and popped on the new unit and bam, done.
If I had a Tig though...
you do know Aluminum can be MIG'd right?
dont know how well it would hold,
all i know is that you use aluminum wire (duh) and straight Argon, instead of c02/ar
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I welded up this one at work one evening, turns out it warped on me a little or something because it lasted about 5 minutes after I started the new engine. It cracked the tops on 3 runners on one side. But I looked cool on the engine stand.