Sorry Pat but I haven't got the exact part numbers for the liner. I'll be pulling it apart and switching back to steel in the next day or so. I'll take some pictures so you've got a point of reference.
I'm using a Binzel torch on my MIG and they are pretty common here in Australia. I'm not sure if the parts are interchangable between torches. I figure each manufacturer will probably have a similar set up.
Binzel have a fairly comprehensive site here:
Binzel
My torch is an older one they don't make any more but the consumables are interchangable with the new torches.
You definitely need straight Argon shield gas. You'll also ne U grove rollers for the aluminium wire. Normal V grove rollers for steel wire will cause you feed problems.
I'm no expert and I'm probably still doing things wrong but I'm starting to get some decent results. Some of the things I've found in my recent round of experementing:
*You need a lot more shield gas. I'm usually pretty stingy with my shielding gas for steel but I had to turn it right up to stop the porosity in the weld with Aluminium. I'm now erunning at about 25 litres/minute.
*You need heaps of current. MIG on aluminium only really seems to work well when you get to spray transfer current levels. This is when the current is high enough that the filler wire explodes of the tip in to fine particles of molten aluminium. This also blows the oxide off the aluminium as you weld. They reckin about 3/16" is about the thinest you can weld in spray transfer.
I've got a 200 Amp machine and I've got the voltage wound way up almost flat out and the wire speed is on about 6 out of 10. I found I wasn't using enough wire at first and had it around 5 and produced some ordinary looking welds.
Prep was done by linishing the parts prior to welding but not much else. I used a clean relatively new regular wire brush to scrub off the soot and oxide that formed on the weld. It comes off pretty easily. A stainless brush would be better.
The angle of your torch is far more critical as is the ength of your arc. I found that it's very unforgiving of lazy technique. If you close your arc up to close you will get aluminium adhering to the tip of your torch and it will jam. If you have your arc to long you loose control of the arc and it jumps all over the place.
Hope this helps.
Cheers