Cast Iron Manifold Modification

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Hello folks Im new to these forums but not mechanical fixes, modifications, etc. I am a big Subaru fan and for a VERY long time now I have been wanting to take a stock turbo exhaust manifold (cast iron ) and modify it to fit my non turbo legacy. This only requires a flange to be cut off and welded back on at a different angle to mate to the rest of the exhaust system. Simple enough? I quickly found out that NO exhaust shop will do this for me not because they can't but because they can't weld to cast iron. So instead of going from shop to shop getting that "stupid" look i figure I should just tackle this myself except i have no welding equipment So my options are find a person to do it here in VA or buy the equipment to do it myself. I have read and read and read and there seems to be the "Hot peening" way then the weld short beads let it cool to room temp repeat until done method.Which would be the best if you were going to do it ? And where are the guys that weld stuff like this  in VA I am kinda let down at the lack of Exhaust shops that can't do this simple mod for me. And for the visual learners  This is what I want to do take the exact same manifold and modify it the exact same way but only for my car. This is a simple 90 with a SS flange welded to a cast iron manifold. Really how hard can it be??
Reply:1-please re-size your images to 800 wide x 600 high pixels--max. This will keep your text from being cutoff the page.If others can read the full text, they will be better able to assist you.Really---how hard can it be?Blackbird
Reply:Cast iron, especially exhaust parts that have been heated and cooled inumerable times, can be very tricky to weld. Clean, clean, clean, than clean again. Preheat and use a high nickel filler material. Sometimes I use a stainless filler.
Reply:Well I would make a suggestion as a qualified exhaust fitter/manufacturer but I would prefer to read everything first.. As Dave said resize the image so the words aren't disappearing off the page..... Good luck!
Reply:I had a 04 STi and did some of my own exhaust parts for it, why not just start with a stainless aftermarket header and start working from there? Much better to weld to and they will flow better than a OEM manifold too.Here is the one I had its exactly the same as the Tomei, GT spec. Looks like you could just cut the flange off and go from there?
Reply:Here's GEE OTTO's text and photo resized: Originally Posted by  GEE OTTOHello folks Im new to these forums but not mechanical fixes, modifications, etc. I am a big Subaru fan and for a VERY long time now I have been wanting to take a stock turbo exhaust manifold (cast iron ) and modify it to fit my non turbo legacy. This only requires a flange to be cut off and welded back on at a different angle to mate to the rest of the exhaust system. Simple enough?I quickly found out that NO exhaust shop will do this for me not because they can't but because they can't weld to cast iron. So instead of going from shop to shop getting that "stupid" look i figure I should just tackle this myself except i have no welding equipmentSo my options are find a person to do it here in VA or buy the equipment to do it myself. I have read and read and read and there seems to be the "Hot peening" way then the weld short beads let it cool to room temp repeat until done method.Which would be the best if you were going to do it ? And where are the guys that weld stuff like this in VA I am kinda let down at the lack of Exhaust shops that can't do this simple mod for me.And for the visual learners This is what I want to do take the exact same manifold and modify it the exact same way but only for my car. This is a simple 90 with a SS flange welded to a cast iron manifold. Really how hard can it be??
Reply:Originally Posted by GEE OTTOHello folks Im new to these forums but not mechanical fixes, modifications, etc. I am a big Subaru fan and for a VERY long time now I have been wanting to take a stock turbo exhaust manifold (cast iron ) and modify it to fit my non turbo legacy. This only requires a flange to be cut off and welded back on at a different angle to mate to the rest of the exhaust system. Simple enough? I quickly found out that NO exhaust shop will do this for me not because they can't but because they can't weld to cast iron. So instead of going from shop to shop getting that "stupid" look i figure I should just tackle this myself except i have no welding equipment So my options are find a person to do it here in VA or buy the equipment to do it myself. I have read and read and read and there seems to be the "Hot peening" way then the weld short beads let it cool to room temp repeat until done method.Which would be the best if you were going to do it ? And where are the guys that weld stuff like this  in VA I am kinda let down at the lack of Exhaust shops that can't do this simple mod for me. And for the visual learners  This is what I want to do take the exact same manifold and modify it the exact same way but only for my car. This is a simple 90 with a SS flange welded to a cast iron manifold. Really how hard can it be??
Reply:The OEM manifold is cast iron.
Reply:Originally Posted by SR20steveThe OEM manifold is cast iron.
Reply:Sorry I couldn't edit the photo bc the edit button was cut off due to my oversized photo :lol:
Reply:Originally Posted by SR20steveI had a 04 STi and did some of my own exhaust parts for it, why not just start with a stainless aftermarket header and start working from there? Much better to weld to and they will flow better than a OEM manifold too.Here is the one I had its exactly the same as the Tomei, GT spec. Looks like you could just cut the flange off and go from there?
Reply:Originally Posted by denrepSaw off the outlet, rotate it, braze it back together... Presto!
Reply:Originally Posted by tanglediver~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~We tried cast iron welding in school. The time to weld cast includes 12 hours of slow cooling to prevent cracking. You need to find someone with the willingness to accept the challenge, try your local welding school, good luck. This is assuming you need a cast iron piece, and not stainless, as Denrep pointed out.
Reply:Originally Posted by denrepHere's GEE OTTO's text and photo resized:Attachment 53013Hello, GEE OTTOIs the proposed cut and weld seen in the above picture? If so, I think you may be dealing with exhaust grade stainless tube, rather than cast iron.Log-on to give us a few more details, and we'll try to pitch-in for a solution.Good Luck
Reply:Ohk so here are my two options 1. The cast manifold modification cut at the red line and weld on a flange that will mate to my stock mid pipe:How difficult would it be to cut at the red line and braze the new flange on? second how strong of a bond will brazing produce?2. Take this SS header and weld a catalytic converter to it and have a mid pipe fabbed :I have both on hand and the SS one is easier I KNOW, but the cast iron will work better for the long term in more ways than the cast unit
Reply:You can't braze this.  I came across this problem on one of our engines at work.  I had to repair a crack in a very thin (.010" 321 stainless steel) expansion joint.  I would have loved to braze it but 1350 degree F exhaust temperatures said otherwise.  We'll just say that I had to make one 50" T weld joining .015" 305 stainless band to a 1/2 inch mild steel flange and one 50" lap weld joinging .015 305 stainless to .010  321 stainless.  It was a long night.  Most braze allows are molten by not much over 1000 degrees F.  Your turbo car engine will see exhaust temps in excess of 1200 degrees F.  You will have to weld.Last edited by 76GMC1500; 07-06-2010 at 11:12 PM.
Reply:Originally Posted by GEE OTTO. . .How difficult would it be to cut at the red line and braze the new flange on? second how strong of a bond will brazing produce?. . .
Reply:Originally Posted by GEE OTTOIf it took you 12 hours then you all were doing something wrong
Reply:Well the Ni-Rod option surfaced when I took to Salem Welding here in salem Va he said he would use the "hot peening method" and Nickel filler the flange is actually T409SUS with a 4 inch long 90 degree 409 piece of pipe (came as a piece). The weld will be isolated from heavy loads and the exhaust temps at the manifold can reach 1000F The optimal temperature the ECU like is around 900F
Reply:Originally Posted by tanglediverOK, all done here.
Reply:Originally Posted by GEE OTTOHey don't take that the wrong way  I know how long it takes with the pre and post heating when dealing with cast.
Reply:Originally Posted by Fat BastardIf you know then why did you come in here and ask?
Reply:If that cast manifold has a cooked, grainy appearing skin to it(which it sure looks like it does), suggest you grind thru that skinfirst-to see what's-what. The Japanese motors are great forcooking the CI manifolds, inside and outside..........So what!......Well, it comes down to whether or not anybodywill be able to achieve anything like some fusion to the parent CI-----and if reasonable fusion does occur, the life expectancy isn't likea new manifold, at all.       Been there and dun that.This is the downside of many CI manifold welding attempts thatyou won't read about-or necessarily be told by a welding shop.Blackbird
Reply:Ok first I don't think you have a clue what you are talking about (Subaru's or welding). Why are you trying to make a modified cast iron OEM manifold with a cat on it? If you want to keep your cat keep the original exhaust in tact. The engineers at Fuji heavy industries (Subaru) are much smarter than you trust me. Do you realize how hot EGT's get on a EJ motor? When I would be in boost my pyrometer would hit over 1400 degrees. I don't think that a brazed joint would be the best performer, I realize yours is NA but they still get very hot. And why do you care how hot your cat gets, are you trying to your part for mother planet or something? I think what you really mean is that a cast iron manifold will hold heat much better creating a faster exhaust velocity helping exhaust scavenging, read below..http://en.wikipedia.org/wiki/Manifol...ust_ScavengingNow another thing Im pretty sure you don't have a grip on is how difficult it is to weld on cast iron without it cracking from heating and cooling. If you want a catted NA header (why I have no clue on earth) use your SS header and weld on a cat like you have showed.
Reply:Originally Posted by GEE OTTOThe weld will be isolated from heavy loads and the exhaust temps at the manifold can reach 1000F The optimal temperature the ECU like is around 900FOriginally Posted by SR20steveTell me why the ECU likes 900F? The ECU doesn't care what your EGT's are...you drive a NA legacy its not like you have to worry about too high of EGT's and detonation from hot turbocharged air. And if thats the case my ECU must have hated me
Reply:Originally Posted by 76GMC1500You can't braze this.  I came across this problem on one of our engines at work.  I had to repair a crack in a very thin (.010" 321 stainless steel) expansion joint.  I would have loved to braze it but 1350 degree F exhaust temperatures said otherwise.  We'll just say that I had to make one 50" T weld joining .015" 305 stainless band to a 1/2 inch mild steel flange and one 50" lap weld joinging .015 305 stainless to .010  321 stainless.  It was a long night.  Most braze allows are molten by not much over 1000 degrees F.  Your turbo car engine will see exhaust temps in excess of 1200 degrees F.  You will have to weld.
Reply:Originally Posted by SR20steveOk first I don't think you have a clue what you are talking about (Subaru's or welding)..
Reply:Third, Thin walled SS manifolds that we (N/A Subaru Guys/Girls) have tried to run dissipate heat too rapidly the exhaust gases are too cool when they pass through the catalytic convert, thus not heating it to the optimal temperature resulting in a MIL, you knew that right?
Reply:@Farmall yeah i plan to wrap the SS option I have on hand with DEI wrap
Reply:Here's my Sti.  '07 SWP   PDX Stage 2 Pro Tuned on 100 octane, Cobb AP, 303 awhp, 364tq.  And yes, this thing moves.     Not my DD, only 5,810 on the odo., and only sees the 100 octane.  I have a 92 Pro Tune map, but don't use it. Invidia TBE, HKS Hi Power exhaust.  SPT SS with TiC Holy Shift kit.  Cusco front & rear sways.  KB endlinks in the rear, stockers in the front.  Stock turbo, factory TMIC.  Sorry for the hijack, but I am an Sti fanatic.  You might want to check out Grimmspeed PnP.  Or they might have something you need on the cheap(er), without the hassle of welding.
Reply:NIce Nice Nice GD right there and SWP is always nice but ima OBP or GRP guy  Grimmspeed doesn't make manifolds they only PnP and coat the stockers then resell them and they do A+ work. Trust me if there was an option on the market i would have been found it by now. I am heading up the UEL ECS project on LGT.com and NASIOC.COM once I get this rough draft finished so to speak i will send it to Stainless Works to be replicated into a production piece. Or i may by the modeler kit and have a CNC facility make one but I def 100% want to do this mod for the Subaru Community they need it, we need it :lol: NICE SCOOB !!!!!