cast iron welding help?

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Hi I am thinking about buying a turbo manifold for my mazda rx7 and I found a manifold for cheap but it needs some repairs as it has some cracks. What is the process of repairing the manifold. Keep in mind these manifolds are like $550 and I do not want to spend that if I do not have to. The pics below show a bunch of brazing beads that takes up a good amount of area but it was done that way because the seller wanted to reinforce the area but the brazing cracked.ThanksRichard
Reply:Take that manifold along with $550 to parts store and exchange them for new manifold. In that fashion you will save time and money.
Reply:For a repair of a cast iron manifold, I'd remove all studs, clean off all that brazing, stop drill all ends of the cracks, U-groove the cracks. Then you use a suitable oven to preheat the entire manifold red hot, and you keep it red hot while you weld the cracks with a O/A torch and a cast iron filler such as Kastweld 111. Once the welding is done, you pack it in insulation (dry ashes, sand...) and let it cool down very slow. Once cool, check the flanges to see if they need re-machining flat.In this case however, with a bunch of failed repairs and cracks going everywhere, you are probably going to be better of if you buy a new one, or just build one  - if you can repair that you probably can build another one.
Reply:One small metal fragment and your turbo is toast.A new one for sure.
Reply:Looks more like mig welds.Heat the manifold on a gas grill, weld the crack and keep the manifold on the grill and turn down the heat slowly.Fast cooling causes cracking.Brazing would work as long as you preheat and do a slow cool down.That crack happened right after welding.If you do have to replace the manifold get a used part.Dealer prices are crazy high.
Reply:Thats not brazing..
Reply:That is the hardest of the cast iron welds, the inside of a circular object.  To make it even worse, it is know to fail in normal use because of poor design.  And then someone who didn't know what they were doing tried to make a repair.  On top of that its a hot service part.  The stars are almost perfectly aligned to predict failure.  If someone has the skill and experience to do the repair successfully, he will also have the judgement to know the repair won't last and recommend a new piece out of stainless steel.  Buy a new or unbroken used one.
Reply:If that came to my shop I'd suggest replacement. A fabricated tube replacement would probably hold up better. If you do try it cut a slot between the 2 ex flanges, do same if you get a new casting.PeterEquipment:2  old paws2  eyes (that don't look so good)1  bad back
Reply:Originally Posted by castweldIf that came to my shop I'd suggest replacement. A fabricated tube replacement would probably hold up better. If you do try it cut a slot between the 2 ex flanges, do same if you get a new casting.Peter
Reply:Originally Posted by castweldIf that came to my shop I'd suggest replacement. A fabricated tube replacement would probably hold up better. If you do try it cut a slot between the 2 ex flanges, do same if you get a new casting.Peter
Reply:I probably will just fab up a manifold out of sch40 304ss. But what if i were to get the manifold and repair it and have a local casting foundry re make the manifold. The manifold is a pretty hard manifold to find as it is a hks part that comes from japan.
Reply:You can try a local foundry to see if they can remake the manifold. Probably better off just going the 304 sch10 route. Cast iron manifolds have there place although in the performance world they have been replaced with tubular manifolds.
Reply:It didn't look like brazing to me either but that manifold is to far gone to try and repair. $550 for a new one is cheap in my opinion.
Reply:nickel rod has worked best for me on that sort of thing, along w/ drill pre heat, peen, post heat, cat litter, everyone described.  not sure how well it would mix w/ whatever filler was previously used.      i'd be asking myself, whats the value of the car, and whats next, before i spent 550
Reply:Hi I will probably just spend the money and make a new manifold. But is there any good sources for 304ss sch 40 as I can not use sch 10 because it is not strong enough as I am using a pretty big turbo. Also I should add that on a rotary engine the exhaust gasses can get up to 1500+ degrees f so I have to use the thicker material.Thanks
Reply:The pic above is roughly how big the turbo is.
Reply:Here is a manifold I would like to get but can not afford right now.LOLhttp://www.turblown.net/store/index.php?productID=4
Reply:http://www.aceraceparts.com/ Is where I purchased all the parts for my manifold. The manifold you listed you could easily make it for a 1/3th or less the cost there selling them for.Here is the manifold I just made for my RB26Millermatic 211Miller Syncrowave 350lx with cooler and tigrunner Thermal Dynamics cutmaster 811955 National Cylinder Gas O/A setup with original patina
Reply:Wow nice job I need to make a rb25det manifold pretty soon.
Reply:So the manifold link I posted it looks like I need 6 90 degree bends also do they appear to be short radius or long. Also it says the manifold has tear drop waste gate tubes so did he make that out of 90s or 45 degree bends.Thanks
Reply:Thanks for the compliment on the manifold. As for your parts, looks like you need 2 long 90s and 4 tight radius 90s and atleast 4' of straight pipe. Although if this is your first manifold you should buy twice as much material for mistakes that will be made. The tear drop wastegates are made out of 90sLast edited by That Guy There; 03-22-2015 at 07:40 PM.
Reply:Originally Posted by bridgeport13b...I can not use sch 10 because it is not strong enough as I am using a pretty big turbo...
Reply:Originally Posted by MinnesotaDaveInteresting that cutting them free is better Must relieve some of the heat/cool stresses or something?
Reply:Hi is the tear drop waste gate 90s made of short or long radius 90s.Thanks
Reply:Originally Posted by castweldCutting flanges loose reduces cracking, GM put a bulletin out on BBC new manifolds to cut them to eliminate cracking.PeterOriginally Posted by bridgeport13bHi is the tear drop waste gate 90s made of short or long radius 90s.Thanks
Reply:Hi just another question what amp should I start at when doing some practice welds on scrap stainless steel, also what filler and tungsten and should I get a nice gas lens.ThanksRichard
Reply:Here is 2 more pics I think the waste gate is long radius 90s Attached Images
Reply:If you've never made a manifold before, I think it would be a lot more involved than you imagine. Bridgeport13b's is very well built but I'd bet he's got some experience building them and knowing how to get everything flat and in the right orientation.