MIG cast exhaust manifolds?

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Hey everyone,I am doing a custom motor project for my Willys jeep and have a question.  The motor I'm trying to transplant into my Jeep, has clearance issues with the stock cast exhaust manifolds.  I would like to cut the manifold after all cyclinder runners collect and turn the rest of the header (piece running to the exhaust flange) to suit my situation.  My question is, can I just MIG weld this together or do I need to do something special?  Thanks,Randy
Reply:if you have the proper filler and gas you prolly could. but i think if it were me id tig it. the spool of wire might be costly when you could buy a pound of so of tig rod. nicklewould be my choice of filler but there are some hardcore cast welders on here who might have a better idea for ya. im trying to get some exhaust info myself!
Reply:Originally Posted by rwirtzfeldHey everyone,I am doing a custom motor project for my Willys jeep and have a question.  The motor I'm trying to transplant into my Jeep, has clearance issues with the stock cast exhaust manifolds.  I would like to cut the manifold after all cyclinder runners collect and turn the rest of the header (piece running to the exhaust flange) to suit my situation.  My question is, can I just MIG weld this together or do I need to do something special?  Thanks,Randy
Reply:If the manifold is cast steel, you will have some measure of success. If it is cast iron, you will have cracking issues really badly with mig.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:I only have MIG available at my home, arc welding at work.  But if I need to control the pre-heat and cool-down temp with ARC that's not feasible either.So, I guess I need to hire someone to do this for me.   What would be the proper prep. for this work?  I need to make the cut and rotate to make it fit, then could I just tack it with MIG to hold it in position to take to a pro?  Should I make beveled edges (v groove) the fitment?Thanks,Randy
Reply:yeah vee the edges, i would not braze it if i were you, once that thing heats up that braze filler could become liquid again.
Reply:Originally Posted by El_Lloydeoyeah vee the edges, i would not braze it if i were you, once that thing heats up that braze filler could become liquid again.
Reply:O/A welding is preferred by restoration shops for that application, followed by some from of nickle based welding/brazing alloy applied either by Arc or Tig. In the case of electric welding pre and post heating are required. Unless you want garbage, then you might as well just Mig it with a spool of harbor freight special wire.[/QUOTE]youre the one talking about O/A welding and brazing alloys so i guess you!
Reply:I've done it with arc and nickle rod. use your gas grill to heat it up then weld a little rite on the grill then heat again weld a little and so on the let it cool down over night on low heat  works great.Life is tuff,so be sharp  lincoln sp 100  cutmaster101  miller bobcat  miller 250 mig  $thousands in snapon
Reply:Originally Posted by El_LloydeoO/A welding is preferred by restoration shops for that application, followed by some from of nickle based welding/brazing alloy applied either by Arc or Tig. In the case of electric welding pre and post heating are required. Unless you want garbage, then you might as well just Mig it with a spool of harbor freight special wire.
Reply:I wouldn't do the "mig thing" on iron manifolds. If the manifolds are more than a few years old or have lots of miles, or were run at high temps,(heavy tow or lead foot) Arc usually won't be a good option. Look at manifolds, if they look almost new, meaning no deep rust pitting, you may get it done with tig high nickel or stick high nickel. When manifolds are badly rusted and thin there is not much iron left to weld. It seems the rust/heat takes out the iron and the carbon stays. Extremely high carbon content makes it hard to get filler to "stick". If you light a tig torch on a old maniflod and try to start a puddle you will get a little ball at the bottom of a hole the rest of the material (carbon) disappears. If this is the case then powder spray will work most of the time- or junk them and get headers.My 2 centsPeter
Reply:I realy think the only way to do what you are wanting to do is O/A and nickel filler you can control it better...I have welded cast iron manifolds with a stick and a nickel think it was a 65 rod it stuck but was real ugly...but then I can't stick weld.....BrandonLincoln Tombstone 225 A/C Steel StickerOld Victor O2/Acetylene setupMiller Syncrowave 250 Tig/PC-300 PulserMiller Millermatic 212 Mig HTP Invertatig 201 Giant Teck D50 Plasma cutterLots of HF grinders
Reply:For a little more background, the engine has 60,000 miles on it, and its from a 1999 Camero.  I would buy some headers but they leave me in the same spot, they are bent for a 1999 Camero, not a 1946 Willys Jeep.  I hate to buy a 500 dollar set of headers, to start cutting them up.  If I could get a new header flange cut out of steel buy a plasma cnc I would do that, but there are currently none in production for this Camero engine.So that leaves me back at my cast exhaust manifolds.  I am getting confused by the posts here, seems like there are two schools of thought.  O/A nickel filler, Arc-nickel rod.I have never O/A welded, so that would be a challenge, even though I would have the equipment at work.  I can Arc weld well, and can also use that at work, however I would need to purchase the appropriate rod.  I also have a bearing heater at work, not sure how high it goes, I generally heat bearing to only 250 deg. F. for interference fit, but I know it goes higher, just not sure how high, I'm not at work now.  So I guess my question is, could I make arc welding work with the proper rod, preheat and cooldown, not ever messing with cast welding before?  And if so what would be the desirable preheat temp., cooldown process and appropriate rod?
Reply:I would suggest that, to get a little background and understanding of what is often involved, you do a search of some posts here, starting with those by Castweld. A few of his have lots of detail.Next, go to a wrecking yard and get a comparable (material and condition) manifold that you can cut up and practice on, using whatever methods you decide will be most suitable for you based on what you learn from reading.  That should at least provide a good beginning.
Reply:http://www.summitracing.com/parts/SUM-G9065/I wouldn't even mess around with modifying LS1 stock manifolds.  You could even buy a flange kit and a bends kit and make your own headers.
Reply:Are you sure nobody makes flanges? What engine is it?
Reply:Originally Posted by rwirtzfeld. . . I would buy some headers but they leave me in the same spot, they are bent for a 1999 Camero, not a 1946 Willys Jeep. . . .
Reply:Originally Posted by Antiblinghttp://www.summitracing.com/parts/SUM-G9065/I wouldn't even mess around with modifying LS1 stock manifolds.  You could even buy a flange kit and a bends kit and make your own headers.
Reply:Originally Posted by rwirtzfeldIts not the LS1, it is the 3.8L V-6, I would have to saw the block of an LS1 in half to get it to fit in my 46 willys, not just the headers.
Reply:Originally Posted by asemasterI've done it with arc and nickle rod. use your gas grill to heat it up then weld a little rite on the grill then heat again weld a little and so on the let it cool down over night on low heat  works great.
Reply:Originally Posted by rwirtzfeld  I hate to buy a 500 dollar set of headers, to start cutting them up.  If I could get a new header flange cut out of steel buy a plasma cnc I would do that, but there are currently none in production for this Camero engine.
Reply:Im not a great welder by any means. But I have been a mechanic for years and I can tell you we used a 110 mig to weld many cast manifolds because we had no other choice.  Many times an ear breaks off (or worse) when trying to remove a broken stud. Many times we have welded a mild steel stud right to the manifold. I even have welded a couple back together from multiple pieces. What we found that worked best is heat it up first. Heat it red with a torch then pull the torch away till the color goes away. Then weld it up with a mig and .035 wire.  It will not look as nice as the welds by the gentlemen around here but if you do your part it wont look terrible and will last quite a while.  It is best to let it cool very slowly. Luckily with an exhaust manifold it is small enough to throw in a metal container and dump a bag of sandblaster sand on it. Im sure the professionals are shaking their heads in disgust at this technique and I can respect that. But when you are working in a commission or flat rate auto shop with customers breathing down your neck wanting their vehicles you have to move a lot of work in and out quickly. No time to send manifold out to welding shop or even order a new one.
Reply:I'm no expert on welding cast but I broke part of my manifold on my truck and all I did was grind a bevel and welded it with stick using a 3/32" 7018 rod. I can't remember if I preheated it or not but would recommend it if possible. I'm not saying this is the right way but stick was all I had and nickle rods were very expensive. that was over a year ago and its still holding strong and didn't look to bad. I don't know if it makes a difference but this manifold was from the '60s. Whatever you end up doing good luck and let us know how it goes.
Reply:I think the reason some of you have had good luck with just regular steel wire or rod is because the repair is at the edge like a tab or something. If you hack something in half and try welding it back up the expanding and contracting will crack a non malleable weld. This is wear the nickel or bronze comes in, it will stretch around instead of just break when part cools down and contracts. So sometimes regular mig could work it just depends on where the break is and what kind of stress will be there.
Reply:Originally Posted by S obsessedI think the reason some of you have had good luck with just regular steel wire or rod is because the repair is at the edge like a tab or something. If you hack something in half and try welding it back up the expanding and contracting will crack a non malleable weld. This is wear the nickel or bronze comes in, it will stretch around instead of just break when part cools down and contracts. So sometimes regular mig could work it just depends on where the break is and what kind of stress will be there.