Weldin cast exhaust manifold

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okay so i have to weld a cast exhaust header. it has a crack in it which someone previously tried to weld and failed. my plan is to grind out there weld and gouge the crack and drill holes at the end of the crack. my question is what is the best way to weld it? also if i remember correctly this will require pre and post heat correct?            THANKS JAYmiller bobcat 250 ntsouth bend metal latheClausing verticle millrikon 17" bandsaweverlast 250exharris oxyfuel set upspeedglass AD helmet with adflo power respirator.
Reply:I have repaired a few cast iron manifolds through the years, almost all with the oxy-acetylene torch and brazing rod. Grind out the crack from end to end, and grind clean an area on each side, about 1/4" wide. I always bolted the manifold to a matching head, to prevent warping. For a cooling medium I used Zonolite isulation, in a container large enough to hold the head with manifold attached. Preheat to around 200*F., and braze the excavated crack area. Try to keep the whole assembly at 200*F., and immediately after braze repair is accomplished, place the whole unit in the Zonolite. covering it completely.It may be necessary to leave undisturbed overnight, to allow slow and complete cooling.Just my $.02 worth...............good luck.Bgbkwndo.
Reply:I would heat it 900 and weld it with NI55.  With proper groove and pre heat it will go on like butter.  Cool SLOWLY.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Thanks fort the info guys I think I'll try brazing I've never done it before thoughJaymiller bobcat 250 ntsouth bend metal latheClausing verticle millrikon 17" bandsaweverlast 250exharris oxyfuel set upspeedglass AD helmet with adflo power respirator.
Reply:Is it cast iron or cast steel?"There are two types of people in America - those who try to classify everyone into two types and those who don't."
Reply:Not sure I have ever heard of a cast steel exhaust manifoldGordie -- "I believe you understand what you think I said, but I'm not sure you realize that what you heard is not what I meant."
Reply:Originally Posted by NiteskyNot sure I have ever heard of a cast steel exhaust manifold
Reply:Pretty sure it's cast iron it's off an old Toyota turbo engine that's going in a woods truck my buddy and I are making.    Jaymiller bobcat 250 ntsouth bend metal latheClausing verticle millrikon 17" bandsaweverlast 250exharris oxyfuel set upspeedglass AD helmet with adflo power respirator.
Reply:Will brazing hold up though? Gas turbo engines can see 1200*F + temps. I would think it would have to be some kind of nickel weld for it to work. Or is that considered brazing also?
Reply:2x on bolting it to a cylinder head.Depending on how you weld it, when the weld cools, there might be enough shrinkage to really pull it out of shape.  Ask me how I know   Depending on the manifold style, you can put some pressure on it and re-heat post weld to get it where it should have been.  On small block chevy, they actually make a turn-buckle looking device to push the  exhaust ports apart a bit.  http://www.amazon.com/Lisle-13000-Ma...ata/B0009OR94WCon Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX
Reply:Cast iron can't warp much, it's so brittle it will crack before it warps.  That is the reason for preheat, to even out the temperatures prior to hot work.  If everything is the same temp it there will be no warpage.
Reply:Hey firedup,Here are some pics of how I do it. "Cold Welding Cast With MIG".Denny Attached ImagesComplete Welding/Machine/Fab. ShopMobile UnitFinally retired*Moderator*"A man's word is his honor...without honor there is nothing.""Words are like bullets.... Once they leave your muzzle, you cannot get them back."
Reply:Originally Posted by yorkiepapHey firedup,Here are some pics of how I do it. "Cold Welding Cast With MIG".Denny
Reply:Last one I repaired, I used the Stoody powdered metal torch.  Manifold has held up wonderfully since and the customer is really happy.  I V'd out the crack with a carbide burr, pre-heated to 400F, heated and spray filled the V'd out crack, put back in the oven at 400F and lowered the temp over 4 hours, then let sit in the oven until fully cooled.  The crack didn't re-form and everything has held quite well (customer has been running the manifold in their daily driver for over a year and a half now).--Wintermute"No man's knowledge here can go beyond his experience." - John Lockewww.improvised-engineering.comManufacturer Agnostic:Blood----------Sweat---------Tears----|------------------|----------------|----Lincoln Red, Miller Blue, Esab Yellow
Reply:okay so today we attempted it. its actually a friends manifold and he wanted to weld it. he mi and stick welded but never ti welded. we ended up usin ni55 rod wit the flux cleaned of to ti it. i told him  to heat the whole part to like 250 300 he only hit the weld area. it kept crackin and it warped it a tiny bit and it looked like cold lapped asss with holes. so i said ill take it n do it so far no preblem its been about 5 hours we will see id say. thanks for the help! jaymiller bobcat 250 ntsouth bend metal latheClausing verticle millrikon 17" bandsaweverlast 250exharris oxyfuel set upspeedglass AD helmet with adflo power respirator.
Reply:Originally Posted by yorkiepapHey firedup,Here are some pics of how I do it. "Cold Welding Cast With MIG".Denny