MIG welding cast iron?

Medium length story short: Offered a free 2002tii exhaust manifold (good) which is on the other side of the country (bad) and has a crack about 1.5" long (also bad). I'm willing to pay to have it shipped here if I have a chance of repairing the crack with my 110v MIG welder, with which I'm a total hack. I know welding cast iron is not going to be easy, but I would like some feedback from experienced welders: are we talking not easy but doable, or don't waste your time and money?

Welding cast iron is sketchy even for experienced welders.  It shouldn't cost much to have someone braze it.

Not easy but doable, I think there are cast iron MIG wires available now.

I've deeply V-ground the crack, stuck it in a gas grill set up as high as I dared, then pulled it out, brazed it, then wrapped it in a welding blanket and stuck it back into the now-off grill to cool down as slowly as possible.  It worked well enough.

I wonder if stainless wire in the MIG would also work given that you normally arc or TIG with a high nickel rod and stainless is mostly nickel.  Haven't tried it.  The key thing is preheating and slow cooling.

Nope. I have successfully welded cast with stick. PITA.

Oh yeah - find the ends of the crack and drill small holes through the, so the crack ends in a nice round not-crack-friendly hole, so it won't grow any worse.  I forgot that part.

Not easy but doable.

I put a propane torch on the area I was going to weld for a bit to get it hot.  Then I hit it with the $90 horrible freight flux core MIG.  It worked.  The things I've welded this way have little to no structural loads though.

Right now I'm only set up with mild steel wire and argon. The cast iron wire is insanely expensive (~$140 for a 2# spool), so that's out; stainless wire is far more reasonable, so I suppose that's the way I'd go - does stainless require a different shielding gas, or is argon OK?

I considered brazing, but is that going to hold up in an exhaust manifold?

This is starting to seem like it may not be worth the cost (shipping cast iron across the country isn't cheap) and effort. But if the stainless option is plausible without additional accommodations it might just keep me interested.

I doubt there is any way that a 110 bolt mig can generate enough heat to do this task.

I have used a mig on cast manifolds in the past. It doesn't go well but has stopped the leak. 

A nickel rod for cast iron is a far better bet and stainless filler with a TIG is also fine. Either way you will have to have the flange ground flat again after.  That heat concentrated into one spot will warp it.

In reply to Jumper K Balls :

That is one advantage of a good strong preheat, you don't need so much current since you won't be losing so much heat to the rest of the metal.

That goes for any kind of welding, really...

02Pilot said:

Right now I'm only set up with mild steel wire and argon. The cast iron wire is insanely expensive (~$140 for a 2# spool), so that's out; stainless wire is far more reasonable, so I suppose that's the way I'd go - does stainless require a different shielding gas, or is argon OK?

You're using straight argon for mild steel? Not straight CO2? I thought the latter was the alternative to Argon/CO2 mix for steel... (I use 75/25, but I am not someone who should be regarded as reference material)

EDIT: I berkeleying hate autocorrect and posting from a phone.

My father broke a $300 manifold on his Kubota zero turn. As in broke the muffler flange completely off. Figuring there was nothing to be lost by trying to fix it,  we dropped it on a old tobacco burner for 15 minutes to preheat it and burned it back together with his Hobart Handler. We gradually cooled it down with the burner and bolted it back together. 

That was 3 years ago. 

I don't know if I would spend money to try it, but I would certainly try it to save some. 

Well, it would be saving money if it works, as 2002tii exhaust manifolds are no longer cheap, and this is free plus shipping, which is (relatively) cheap. It's not a massive crack - maybe 1.5-2" max, from #3 runner to the plenum - so it's not like I'd have to put two halves back together or anything. With a good preheat on the gas grill it sounds plausible, even with less than ideal equipment.

I'd have to look at the tank - it's been a long time since I filled it - but I think it's 75/25 argon/CO2, IIRC.

Worst case I suppose, I find someone local to weld it up.

Acr works best. preheat is a must.  Forney sells NORM-A-CAST rod for thing your not going to machine and another if your in need of machinable but ive only used the normacast and it works great.  

Manifold see lots of heat cycles and rapid temp changes there not the easiest but doable for sure.

Turbo Yoda's method.