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Old 09-22-2013, 01:25 PM   #1
2JZ
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Default Stock Headers cast iron flange failed...

I have a JDM STi motor (ej207) with OEM twin scroll headers. The pipes appear to be mild steel tack welded to a cast iron flange. Somehow the welds failed and I can literally could pull the whole pipe out of the flange

How should I fix this! Local shop said their welder is not good enough and they're going to need a special welder or some rods? I'm worried that the repair won't hold the extreme temperatures a protuned turbo car produces. Car is winter driven too...

Maybe I can cut out the flange and replace it with a stainless steel flange?




Many will suggest to go with aftermarket headers however, the stock headers are a very good design. Tomei makes the best replacement headers but advertise only ~10whp gain only after 5000rpm.
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Old 09-22-2013, 03:25 PM   #2
RockNRace03
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cast iron or cast steel? cast iron seems odd if it was a factory piece. if so though there are ways to do it. a few good tacks and maybe braze the inside of the ports for a good seal? a local welding shop should be able to give it a try
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Old 09-22-2013, 06:45 PM   #3
kellygnsd
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Quote:
Originally Posted by 2JZ View Post
I have a JDM STi motor (ej207) with OEM twin scroll headers. The pipes appear to be mild steel tack welded to a cast iron flange. Somehow the welds failed and I can literally could pull the whole pipe out of the flange

How should I fix this! Local shop said their welder is not good enough and they're going to need a special welder or some rods? I'm worried that the repair won't hold the extreme temperatures a protuned turbo car produces. Car is winter driven too...

Maybe I can cut out the flange and replace it with a stainless steel flange?




Many will suggest to go with aftermarket headers however, the stock headers are a very good design. Tomei makes the best replacement headers but advertise only ~10whp gain only after 5000rpm.
Find a better weld shop. At least they were honest with you instead of just attempting the weld and messing it up.
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Old 09-22-2013, 11:48 PM   #4
crazychrisra
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I weld cast steel to mild steel quite often at work. The trick I use is to preheat with an oxy/acetylene torch before welding. I have yet to have a weld break on me. I use this technique on suspension on heavy duty manure spreaders. It should work for your header as well.

Chris
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Old 09-23-2013, 12:15 AM   #5
Baja1000
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As stated earlier "cast iron or cast steel?". There is a big difference between them and their weldability. It also seem unlikely to me that the factory would pair mild steel or cast steel to cast iron. Cast iron doesn't like to be welded very good. There is a procedure to follow if you want to even consider it to work and hold, and that's just welding cast to cast. There are different grades of cast iron too. You do have to use specialty welding rod tho. Never heard of having to use a special welder to weld cast. Another thing that happens to cast when it goes from hot to cold a lot is it flexes and changes matallurgically. The carbon from the exhaust permeates the cast to the point where it cannot be welded in any way. It vaporizes when an electric arc hits it. It becomes mostly carbon instead of cast iron.

As for brazing the two together I would have to discourage doing that. Unless you use a high temp brazing rod you could run into the problem of the joint still coming apart due to the high temp of the exhaust. The exhaust could melt the brass due to its low melting point. So you would be back to were you started, broken exhaust.

The other possible fix is what you mentioned, using stainless flanges. This is a good fix as the stainless is durable to corrosion and heat, and you can weld mild steel to it. On the flip side you will run into what is called electrolysis. The two different metals cause a chemical reaction with each other and breaks down the metal between them, it will rust a bit faster. That's why you don't see a lot of steel and stainless steel together without an insulator between them. It might cost you a little bit to fix either way, something to keep in mind.

This is just what I have found in my 22 years of being a welder/fabricator. Hope this helps you to figure out what you want to do.

It might be better to get aftermarket or new OEM rather than fix the old, IMO.
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Old 09-23-2013, 12:22 AM   #6
Baja1000
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Double posted for some reason

Last edited by Baja1000; 09-23-2013 at 06:08 PM. Reason: Deleted double post
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Old 09-25-2013, 08:32 AM   #7
2JZ
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Quote:
Originally Posted by Baja1000 View Post
As stated earlier "cast iron or cast steel?". There is a big difference between them and their weldability. It also seem unlikely to me that the factory would pair mild steel or cast steel to cast iron. Cast iron doesn't like to be welded very good. There is a procedure to follow if you want to even consider it to work and hold, and that's just welding cast to cast. There are different grades of cast iron too. You do have to use specialty welding rod tho. Never heard of having to use a special welder to weld cast. Another thing that happens to cast when it goes from hot to cold a lot is it flexes and changes matallurgically. The carbon from the exhaust permeates the cast to the point where it cannot be welded in any way. It vaporizes when an electric arc hits it. It becomes mostly carbon instead of cast iron.

As for brazing the two together I would have to discourage doing that. Unless you use a high temp brazing rod you could run into the problem of the joint still coming apart due to the high temp of the exhaust. The exhaust could melt the brass due to its low melting point. So you would be back to were you started, broken exhaust.

The other possible fix is what you mentioned, using stainless flanges. This is a good fix as the stainless is durable to corrosion and heat, and you can weld mild steel to it. On the flip side you will run into what is called electrolysis. The two different metals cause a chemical reaction with each other and breaks down the metal between them, it will rust a bit faster. That's why you don't see a lot of steel and stainless steel together without an insulator between them. It might cost you a little bit to fix either way, something to keep in mind.

This is just what I have found in my 22 years of being a welder/fabricator. Hope this helps you to figure out what you want to do.

It might be better to get aftermarket or new OEM rather than fix the old, IMO.
''

thanks for this reply. I have no idea about the material of the flange to be honest (I know nothing about welding and types of metals) but the welder said the flange is very hard to weld and it wouldn't stick. They ended up renting a huge (arc i think) welder that was in a pick up truck. They still had huge issues making it stick! All in all it was 'fixed' but they told me to get a new manifold asap
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Old 09-28-2013, 01:41 AM   #8
Baja1000
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Your welcome. Anything I can do to help in answering your question. I'm surprised the shop was able to get it to stay together with the amount of problems they had according to your reply. It sounds like the cast iron flange was starting to become more carbon if it was that difficult to weld already. They also might not have had the right welding rod to do a proper weld job, hence the difficulty in getting it to stick or weld together.

You are right in the type of welder they would have used. Another name for it would be a "Stick" welder or the industry name SMAW - "Shielded Metal Arc Welder", just an FYI for you. I am surprised they would have had to rent a welder that was in the back of a truck tho. Wouldn't need that big of one, unless that's all they had access to.

I will have to agree with the weld shop on not waiting to long to get the exhaust manifold replaced. It probably will not last very much longer before it breaks again.
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