Help with mild steep exhaust manifold

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Hello Guys.Great forums.Im definitely not a professional welder, I have did some welding on cars (as in rust removal/welding panels), with decent results, but with this particular job my skills are inadequate and I was hoping knowledgeable people might be able to offer some advice. To make it harder I only have  access to a 130A gasless mig, but then again penetration is adequate and splatter is not an issue for me.As a part of turbo setup, I have build a turbo manifold some time ago. Its made out of sch40 mild steel steam pipe. I do realize that this is not the best design as far as turbo manifolds go, however space constraints and access issues have forced this type of design.Consider the pic below. It has cracked before and it was re-welded in 'C' and 'D'. It's cracked again, all though cracks are very thin. Should I cut this with a cutoff blade and weld with the gap or should I just lay a bead on top of the crack ? I my prior experience either form of welding causes shrinkage as the weld cools effectively causing head flange to bend outwards.But the main issue is that when I'm welding in point 'A', the cylinder head flange bends (see point 'B'). What could I do to prevent that from happening ? I can weld in temporary brace, but afterwards it would have to be removed as that where the exhaust pipe goes... I have cut that whole joint off (part of the cut is visible near 'A') , clamped the flange flat and welded, but again, as the weld cools the flange bends :/ How about cut at 'A' again, instead of bolting the flange flat, bend it the other way, so that onceimage attached:I do know that flange will have to be machined flat, which is not an issue, but still i would like to get it roughly straight, as this flange was machine once already and Im affraid that after next cut there wont be much 'meat' left there.Input much appreciated.Thanks in advance, Matt.
Reply:You'd better use the proper filler for the crack's reweld. For the deformation,you can do as the following picture.
Reply:I use steam pipe almost exclusively due to the cheap cost and availability of weld els, so no biggie there. I bevel and tig them, but mig should work fine. They suck up a bit of heat, but after they are warmed up they seem to work pretty well.I've always had the advantage of bolting the manifold to a spare head before welding. This seems to help keep things straight/flat. If you have the time, perhaps a large chunk of steel drilled for the mani.I'm not crazy about your wastegate placement...probably due to space, but it looks like the left 3 cylinders will have trouble venting through the output of the right three cylinders....looks like an unbalanced will result. Maybe I'm seeing it wrong...hard to see in pictures sometimes. Is that a tie in to the wastegate from the front three going 'straight into' the wastegate?What's this on, a I-6 BMW or something??ChayLast edited by miller300a; 05-13-2014 at 06:39 PM.
Reply:Hello.Thanks for the tips:CN_SAW: I'd like to avoid cutting this as welding in that stop causes shrinkage and results in wrapped flangeMiller300A:Yes, it's a straight 6 BMW m20 engine in a e30 3 series. Wastegate does great work of controlling boost, perhaps that particular photo angle is not the best. It's a custom WG setup where WG valve is divided (for the twinscroll turbo), but services with a single valve.Also, I also always blot the work to a flat surface, if you look at the pic, there's a fat mild steel channel section in the vice which the manifold is bolted to to remain flat. However after welding, once i release the clamps the manifold always bends upwards.Upgate on the project:I took it to a friend who TIG welded it. To avoid wrapping of the flange, manifold was cut again then welded in a way where the flange was clamped in a position that it was bent the other way, so that after welding shrinkage caused flange to straighten.Hard to say whats gonna happen after few good heat cycles....