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Thread: Is this easily repairable?

  1. #1

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    Is this easily repairable?

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    So I've got a cracked manifold in a pretty easy to get to spot. I'm curious if I can get the truck warmed up and use brazing rod to seal it up enough to stop the leak temporarily. Would the manifold get hot enough to melt the rod or would it have to be welded as a permanent fix? The main reason I'm worried is because it's before the O2 tricking it and giving me a CEL and MPG is terrible. I'd prefer not to have to replace it because 1: new isnt available and 2: I'm not sure how well the bolts on the bottom will come loose without breaking so I cant remove it to have it welded. I've fixed stamped steel headers with brazing rod before but Idk about cast iron.
    My biggest fear is there was only the one crack when I first saw it. Driving the truck more have appeared. I'm worried welding or sealing the holes won't really help but make more cracks appear.

  2. #2



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    Cast Iron can be welded, but it almost an art form - not for the faint hearted. Brazing will not work, if you got it to stick it would not stay because of the metals being dissimilar in composition and expansion / contraction rates.
    Pennyman1
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  3. #3

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    That's what I thought. Most people in my area won't even try to weld cast iron. Not to mention more cracks are appearing and spreading. It may be a better idea to find another manifold.

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    Trick to welding cast iron is to get the entire piece damn-near cherry red hot. All of it. Then use an oxy-acetylene setup to make the weld.

    I have done it myself (with one success out of several tries), but not being a pro, it will be REAL hit or miss. Also have to be careful to cool the piece nice and slow when yer done.

    Even pros hate doing it because of the fact cast can have a lot of imperfections (bubbles) and sketchy alloys.

    If you want to try it, remove it and put it on some bricks. Get a propane torch (the kind they use for weeds and burning asphalt), then heat the hell out of it, weld with absolutely minimal filler, then anneal it again. Once yer done, get it covered and out of any wind or cold air, any stresses from the weld or cooling too fast will cause it to crack. Then cross your fingers it worked. I think you can do it with arc or mig/tig but was always told to use O-A.

  5. #5

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    You can weld over that crack using Ni-Rod. The nuts holding the manifold on should come off easily if you heat them with an acetylene torch and then turn them off the studs. Heat the manifold slowly and evenly to about 900 degrees F. and use a Tempil stick to ensure you have the same temperature all around. Have your welding rod ready to go as the manifold, being quite thin, will cool quickly once you stop heating it. Use the softer Ni-Rod at the lowest current you can and weld over the crack and on both sides of it.You may want to bring it all back up to 900 degrees when the welding is done and then wrap the manifold in an insulating blanket to allow it to cool slowly. Check the mounting surface for flatness with a straight edge after it cools. If there is any warping you may have to have it machined flat for it to seal properly against the head.

  6. #6

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    I've contemplated just getting another one til I found this.. wtf lol I think i'll scout the junkyards. I know where one is. I wonder if anyone on the site has one laying around.

    http://www.ebay.com/itm/MITSUBISHI-M...d76515&vxp=mtr

  7. #7



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    That guy is on crack, and not the ones in your old manifold.
    Pennyman1
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  8. #8

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    I was thinking cast iron had to get alot hotter than that and i was aware of the air bubbles. They can pop and damage the manifold further. thats why most dont try.

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    I have heard of some shops heating the piece in an oven before welding it. Bigger issue is will it start to crack again later.
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  10. #10

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    It may crack again later if it cools too fast as this will cause stresses in the casting. You can use pre-heat as low as 500 deg. up to 1400 deg. max. The pre-heat is to prevent the casting from sucking the heat out of the weld to quickly making it brittle, and prevent the weld from heating up the casting to rapidly in a localized area. When I make repairs to cast iron gearboxes I shoot for around 900-1200, but then the gear boxes are probably thicker than a manifold. Too hot and you risk blowing a hole as soon as you strike the arc. The area around the weld will heat up more than the rest of the manifold as you weld it, and after a few welds it will be red hot. As far as the bubbles go, if you get them, grind them out and weld again. Keep repeating this until the bubbles stop appearing. If it starts to get too hot, let it cool a minute or so between welds..... Without experience I would recommend finding a manifold from a scrap yard or somewhere. Then take your cracked one and try welding it.

  11. #11

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    Good info, Andy 2. Was always told to anneal (reheat to relax any metal stresses) the piece after it had cooled slightly before covering/wrapping it for final cooling, though.

    This said, "I was always told" by my 85+ y/o grandfather who was a GM mechanic's instructor for 40 years. He is old-school and set in his ways. Same reason for insisting on using gas, he has a shiny fancy Miller MIG in his hangar that's barely been touched (mostly by my Uncle and I).

  12. #12


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    you can mig weld cast but you must use a Ni-rod wire and as everybody said you have to preheat the part with a tiger torch or Oxy/Acet with a rosebud tip. grind a V into the crack then fill with mig.

  13. #13

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    We need to talk camoit into getting the headers cheaper :p lol that'd fix the problem. I want a set bad but just cant drop that into the truck right now. The car needed tires from tax money more since I have been (and probably will start doing again) driving 80 miles a day

  14. #14



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    Quote Originally Posted by recian View Post
    We need to talk camoit into getting the headers cheaper :p lol
    Ya the only way we are going to get the price down is by selling them and getting production up. If he builds 5 at a time is would reduce the cost. But he had about 1 week in just building the jig and getting the header plates programed into the CNC machine. It's like the body for my truck. Now I can build them all day long at a reduced price since I already spent the money to build the fiberglass molds.
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  15. #15

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    i know this is just the perfect excuse to put headers on the truck just not an excuse to put that kind of $$. I could get my body straight for that. Found a guy with a good bed within a few hours for $175

  16. #16

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    So... I was at the junkyard today and found another 2.4 truck. Guess what?! the manifold on that truck has a weld in the SAME spot where my crack is. (it was a poorly done weld) It also runs down the side of the manifold. I'm starting to think it's a defect in the metal that shows itself with age.

  17. #17

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    Being as that manifold is cracked you could probably get it real cheap and try to fix it better than the last guy. If you're successful you can swap it for yours with minimal down time and not a lot of cash.

  18. #18

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    Junkyards dont care if theyre cracked or not in prices. Also I'd rather not follow up somebody else's mess. I'd rather find one that's good or not molested and fix it the way I want.

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