Mig welding aluminum..........

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I'm building an intake and need some way to weld it up. Can't really afford a tig welder but I do have access to a mig with spool gun. Why do people keep telling me it's not wise to use the mig on aluminum?? I'll be welding 3/8" 6061 with it. It's just an intake manifold so I don't need full penetration, just needs to be air tight. I mig weld (production/factory) for a living so it's nothing new to me but I've never welded aluminum. Seems like the main thing is making sure the aluminum is clean clean clean.I've been looking at tig welders on ebay, if I was to buy one what kind of amperage do I need to weld something that thick?
Reply:MIG works great for aluminum, I don't know why anybody would say otherwise.  They probably just want you to pay them to TIG it.
Reply:i built a intake from scratch and a tig is the only way...there is just some places a mig tip will not fitand there is no adjustability like there is with a foot pedalyou are in for major disapointments i'm afraid ...zap!
Reply:Zap,Would it matter what kind of car the intake is meant for?  I was just thinking that a simple little 4 banger intake might be ok with mig...Not that I am planning one or anything....just curious.Smithboy...if it ain't broke, you ain't tryin'.
Reply:This isn't yer typical sheet metal intake, there really isn't any hard to reach places with it. I definitely understand about the adjustability of a tig though. I'll post a pic of the intake when I get home from work in a few minutes and give you a better idea of what I'm working on.
Reply:Here's what I'm working on, there really isn't any hard to reach places. Again I know nothing about welding aluminum so I'm clueless. I've talked to several people about it the last few days and get a different answer from everybody. One says I need at least a 300 amp TIG welder, one says something like a 185 amp MIG welder would do it, one told me the 185 would do but I need to preheat it so I really have no clue and I damn sure can't afford a 300 amp TIG welder. Do I really need full penetration just for an intake manifold??
Reply:yes you want full penetration and mig will work great on that or dc tigChuckASME Pressure Vessel welder
Reply:Well, hmmm.  I'm outa my league here, in terms of "what to do's" for building intakes...Zapster has experience...maybe do others also, but, with all the conflicting points of view (some you mention, some are mentioned here), there is probably some experience with failure in a project like this using mig.  I'd also say that with all the variables associated with welding aluminum, this would seem to be a pretty tough (more like unforgiving) first shot at aluminum, regardless of which process you choose.The mating surfaces arent too complicated...but controling heat will be an issue (warping).Have you thought about a mockup or a dry run?  Get some extra scrap metal and just try to build it.  You have access to the welder.  As long as you dont have any irreplaceable parts involved, consider it you interduction to aluminum mig.Just a few things to consider.Smithboy...if it ain't broke, you ain't tryin'.
Reply:I do have some scrap aluminum that I was planning on practicing on just to see how I need to set the welder up before I weld on the "good" pieces.  I've been looking at welders online and I might just bite the bullet and buy one. I've been looking at the ESAB multimaster 260, anybody got any experience with these? It's 300 amp max with a 50% duty cycle at 260 amps. Reason why I'm looking at this one is it's MIG, TIG and stick, all in one. Seems like I have an uncle that has one similar to this and he's a sales rep for a welding supply company, might have to give him a call. Decisions decisions!!
Reply:Originally Posted by IMAWELDERHere's what I'm working on, there really isn't any hard to reach places. Again I know nothing about welding aluminum so I'm clueless. I've talked to several people about it the last few days and get a different answer from everybody. One says I need at least a 300 amp TIG welder, one says something like a 185 amp MIG welder would do it, one told me the 185 would do but I need to preheat it so I really have no clue and I damn sure can't afford a 300 amp TIG welder. Do I really need full penetration just for an intake manifold??
Reply:There's really no need for runners in a  blown application especially with port injection, look at some of the old B&M blower manifolds, no runners and that's with a carb setup. Is it the most efficient setup? Probably not but I need all the room I can get with the car this is going in, I don't want to have to cut the cowl.Anyway, does anyone have any comments on ESAB welders? Just talked to my uncle and he can get me whatever I want at his cost. Is 300 amps enough for this job? Are ESAB welders junk, I've never welded with one before. I would like for this to be the only welder I have to buy for a long time. Zap, you got something against chebby's? Thems fightin' words! haha Thanks guys, you too zap........... haha just kiddin'.
Reply:Zap, you got something against chebby's? Thems fightin' words! haha Thanks guys, you too zap........... haha just kiddin'.i bleed ford blue i can't elaborate on anything esabnever used one so................is that the motor its going on?tell me its just the mock up let us see pics and tell us of your adventure as it goestoo bad  i did'nt do that when i built the ones i did    ...zap!
Reply:Oh man I can't even talk to you then if you bleed blue!!! What can I do to make you see the light man???  That is just an old block and heads I had laying around I'm using for a mockup. It's going on a 96 Trans Am LT1 350, very little room under the hood. Just talked to my uncle again and the ESAB welder is out. It's not AC so no aluminum tig. He's got a plan though, we'll see how it goes.I'll keep yall posted as it goes, don't know exactly when I'll get to weld it up though.
Reply:...zap!
Reply:There's no reason why you couldn't weld that up with a spoolgun.  Full penetration isn't so much of an issue since it's not a structural part.  The only two issues to be worried about are that it is sealed completely and that warpage isn't an issue.  Preheat can help with the distortion whether it's TIG or MIG welded.-Heath
Reply:That's what my uncle wants to try, pre heat then mig weld. Hope it works cause thats alot of machining time ruined if it doesn't work.
Reply:It might be wise to leave some tolerance and then do some post-weld machining.  It certainly depends on what setups you can do, but it might be wise to surface mill the mating surface of the intake manifold after it's been welded.-Heath
Reply:I'll definitely have to machine the mating surfaces after welding it up. Ever heard of a billet manifold? Just a lill thought in my head right now. I might make another one similar to this out of one piece and then bolt a top onto it, that way I won't need to weld anything except the injector bungs. It'll have really short runners zap, just for you!!  hehe
Reply:Just out of couriosity, are you going to bolt the pieces in...THEN weld?  Or, are you welding, and then bolting in.  I was just thinking that if you had an old junk motor (of same type) laying around somewhere, it might make a good clamp/jig to hold everything in place and minimize warping.  I am not sure I would weld in-place on the motor you plan to use, though.  Just a passing thought...What do you experienced manifold builders think of this???Smithboy...if it ain't broke, you ain't tryin'.
Reply:The motor it's sitting on now is my jig. I'm going to weld the bottom and two sides with it on that motor then tack the top on real good and take it off and weld the top and ends on it.