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View Full Version : Turbo headers: mild steel or stainless



BigBlockOlds
08-23-2005, 05:47 PM
Just wondering if, as long as you have mild steel coated with Jet-Hot or similar product, will it hold up to the exhaust temps of a turbo setup as well as stainless?
Thanks,

chicane67
08-23-2005, 08:05 PM
Uhhh. You did just say squirrel headers, ..... Id say stainless 304 at a minimum, if not 321, or at least just for the flanges themselves.

Or if you really up to it how about inconel ??

You will dis-color Jet-Hot or Olympic or any other ceramic coating with the use of squirrels, just from the saturation temperature under moderate boost.

Ralph LoGrasso
08-23-2005, 08:32 PM
Uhhh. You did just say squirrel headers, ..... Id say stainless 304 at a minimum, if not 321, or at leastr for the flanges themselves.

Or if you really up to it how about inconel ??

You will dis-color Jet-Hot or Olympic or any other ceramic coating with the use of squirrels, just from the saturation temperature under moderate boost.


Oof. Isn't inconel like $373.48 a foot these days? I'll agree with Tom on this. If you're going with Turbos, don't skimp, go with 321 stainless.

parsonsj
08-24-2005, 06:41 AM
Yup. Mild steel will not make it. If in doubt, have a look at the video of the Mule's headers on a recent chassis dyno. They turned orange from the heat. I don't think anybody's header coatings can handle that.

jp

myclone
08-24-2005, 06:53 AM
Oof. Isn't inconel like $373.48 a foot these days? I'll agree with Tom on this.

It aint cheap... At work we use several "muffles" (basically rectangular tubes) which are inconel that are 20'L X 8"W X 4"H and the wall thickness is about 3/8". The replacement cost is $10k each and we have 4 of them that get replaced about every two months or so.

YEEEOUCH!!!

IMO inconel is over kill for anything thats street legal 321 is your best bet if you have the extra dollars to spend but if youre pinching pennies then 304 is fine if the welds are quality work and some thought is done on tube placement to ease the expansion stress from the heat.

I built a set of turbo V6 headers from 16 guage mild steel and had them coated with the high temp (2k deg) ceramic coating and they held up fine. Of course the longest the engine stays WOT is 1/4 mile so the mild steel doesnt really get hammered continuously with high heat which IMO is why they are still alive. Next set I do will be 304 as soon as that money tree thing takes off and I can pick up a TIG welder.

My .02

CamaroAJ
08-24-2005, 08:55 AM
can you mig weld a set of turbo headres? or is that not recomended? i'm going to build mine with 321 also.

Supra510
08-24-2005, 09:30 AM
You can make them out of mild steel using weld els. These are 90 degree smooth (mandrel type bends) that are 1/8 inch wall thick. You can use these with schedule 40 straight pipe (also 1/8 inch wall). All available at McMaster or your local industrial plumbing outlet.

Pic of mine after I wrapped it:

https://static1.pt-content.com/images/noimg.gif
It actually weighed about the same as the stock cast iron manifold. Search Google for weld el manifold you'll find a few examples.

Anthony
http://www.cardomain.com/ride/674663

Fuelie Fan
08-25-2005, 08:01 PM
It's not just the material, it's the design. If you use thick wall as mentioned above, mild steel works. Heck, with enough mass, cast iron works (see any OEM setup). But, if trying to reduce weight, then progressively higher quality materials will be required.

08-25-2005, 08:38 PM
can you mig weld a set of turbo headres? or is that not recomended? i'm going to build mine with 321 also.

Use 347 filler and preferably tri-mix gas and don't look back. As with TIG, you will have to purge the inside of the tube.

jakespeeds
08-26-2005, 05:01 AM
You're doing a non intercooled setup on a 7M? Do you have it running yet?

Jake




You can make them out of mild steel using weld els. These are 90 degree smooth (mandrel type bends) that are 1/8 inch wall thick. You can use these with schedule 40 straight pipe (also 1/8 inch wall). All available at McMaster or your local industrial plumbing outlet.

Pic of mine after I wrapped it:

https://static1.pt-content.com/images/noimg.gif
It actually weighed about the same as the stock cast iron manifold. Search Google for weld el manifold you'll find a few examples.

Anthony
http://www.cardomain.com/ride/674663

Supra510
08-27-2005, 12:38 PM
I have it running. Just did a track day at PIR yesterday. It is intercooled (air to water). Here is a pic of the completed engine bay. You can see more pix at the site listed below.


https://static1.pt-content.com/images/noimg.gif

Anthony
http://www.cardomain.com/ride/674663

jakespeeds
08-27-2005, 01:41 PM
Very cool. PT a little differently. I have a 73 SS nova that is going full out but I also have a highly modified 88 turbo and a 85 Supra going turbo. Car looks bitchen.

Jake

Supra510
08-27-2005, 06:09 PM
Thanks, finally about finished with the mechanical side, or so I thought 'til the clutch started slipping at 17psi at the track day. Had to turn the boost down. I'm running the W58 trans and I think it's giving up the ghost as well so looks like an r154 and new clutch are in the works before next track day season. Good news is I can still drive it fine and run any kind of autocross without any issues the way it stands. It's always something.

Anthony
http://www.cardomain.com/ride/674663

Fuelie Fan
08-27-2005, 06:39 PM
why'd you put the thermal wrap on the compressor outlet???

Supra510
08-27-2005, 09:09 PM
To keep heat out of that pipe. You might be thinking that I'm keeping it in (since that's what it does for the exhaust), but it does a good job of keeping the heat from the engine bay out as well. There is a bare spot on the pipe right by the intercooler. Prior to doing wrapping the pipe it was so hot in that area that I could not touch it even after normal driving. Now I can easily touch it. Would probably work even better if I wrapped it in something reflective, but I haven't needed to at this point. It gets really hot in there at track days. I have all my exhaust wrapped including the turbo and I've still melted plastic wire covering (whatever that black stuff is called) that is 8-10 inches from anything.

Anthony
http://www.cardomain.com/ride/674663

Fuelie Fan
08-28-2005, 09:18 AM
I STILL think you may be keeping it in. at 17 psi boost, you're looking at discharge temps of about 100C even with 100% efficiency (which you know you don't have), and at part throttle you don't really care if you're heating it or not. Just becuase you can now touch the pipe doesn't mean you've improved the situation. I'd reconsider, or at least take some measurements if i were you. I think you would find that you would be better off employing heat shields (if necessary, it doesn't look like the intake has a line-of-sight to the exhaust) and controlling underhood air than using thermal wrap, imo.

They make two grades of corrugated loom, by the way. The high temp stuff usually has a gray stripe and is good to 150C, the other stuff melts at 90.

Supra510
08-28-2005, 04:07 PM
You may well be right, a thermocouple would tell the tale. It probably doesn't matter that much one way or the other, it's not like boost is in the pipe very long. I just figured I'd rather have a cooler pipe to start with and this seems to do it.

Anthony
http://www.cardomain.com/ride/674663

Fuelie Fan
08-29-2005, 07:06 AM
yeah, it's hard to say, but if you think about it, thermal wrap makes the exterior of your exhaust "feel" cooler while simultaneously keeping the exhaust gasses HOTTER by inhibiting heat transfer to the surroundings. This is what i was getting at by saying that just becuase the wrap allows you to touch the pipe doesn't mean it's actually doing anything beneficial. If i was at home i could guesstimate it (actually prob not, i have no idea about airflow rates across that tube underneath a hood). You're probably also correct that it's probably not a big deal either way, but if you're gonna do it, might as well do it right!

my72vette454
08-29-2005, 04:40 PM
I built a twin turbo setup on my big block vette last winter. I was going to use stainless but decided to do it out of mild steel first to see how it would work. I have been running it this summer with no problems so far. I want to redo it out of stainless some day and it will be easier since I have patterns now. If you want to experiment with your setup first I would suggest doing it with mild steel as its lots cheaper and easier, then when you get it how you like it, go with stainless.

Mike

primate
08-29-2005, 07:34 PM
i have read that mild steel is fine as long as you have the turbo supported also with a simple bracket that takes the stress off the header.

thats the way i am doing mine, mild steel thats been ceramic coated. i dont have the ability to back purge the material to weld stainless...

08-29-2005, 08:34 PM
i dont have the ability to back purge the material to weld stainless...

If that's the only thing holding you back, go to your friendly local hardware store and rig yourself a Y-fitting off of your regulator, with a ball valve in the purge line. That's not the preferred way to go about a purge line, but it works. The correct way, if you're wondering, is with two bottles and two regulators.

myclone
08-30-2005, 03:32 AM
Use 347 filler and preferably tri-mix gas and don't look back. As with TIG, you will have to purge the inside of the tube.

Matt,

Ive never tried to do any SS MIG work and was wondering if you have any suggestions on where to start with heat/wire speed/torch speed/sheilding gas CFM/etc.

I cant ever seem to catch a nice TIG in my price range when I have the money and the situation at work has changed in that I cant use their TIG anymore but I already have a nice MIG in the garage I wouldnt mind giving it a shot to see how it turns out. Some input from someone thats already BTDT would be appreciated to maybe help with the learning curve though.

BTW, if you'd rather not hijack the thread with welding info feel free to PM me but I bet the ppl who are reading this thread would be interested in any info as much as I am.

TIA

08-30-2005, 08:18 AM
I think the biggest problem you'll face is just the fact that you'll be welding 16ga butt welds with a MIG, stainless or not, in a small tube weldment. Your travel speed will have to be up there, and your fitup will have to be near perfect.

Definetely use .023" wire! ER308 for 304 tubing or ER347 for 321 tubing.

If you have a machine that has voltage and wire speed displays, I think I would start at around 13.5V and 135IPM. That's a wild guess, as I don't do much thin stuff with MIG.

You'll be looking to get a setting that obviously doesn't burn through, but that does produce 100% penetration. You'll also be looking for some color in the weld. Any welds that are flat grey, and you've lost all of the material's corrosion resistance, and have a very brittle weld. That condition on a header is a garunteed failure.

Unless you'll be using a spoolgun with a two stage trigger to post-flow the weld, the ends of each weld will turn flat grey. It's just a fact of life with MIG on stainless. (Also one reason that MIG on 4130N isn't recommended.) For the intermidiate stops along the weld, immediately brush the weld with a stainless steel wire brush used for nothing other than stainless, until the weld is silver. Do this while it's still hot! When you start your next weld, be sure to whip back onto the end of the previous weld, then continue regularly. This technique is kind of a band-aid, but in reality I've never had a failure doing it this way. To my knowledge, the city of San Fransisco's stainless drinking water filters that I welded are still doing fine.

Don't be surprised when the filler transfer sounds different than you're used to hearing. Stainless has a softer sound to it by nature, and I have a hunch that with the voltage/wire speed it will require, you'll be in what's called globular transfer. If that's the case, you'll see the end of the wire ball up and then drop into the weld.

myclone
08-30-2005, 07:07 PM
Simply awesome...exactly what I was looking for.

Thanks Matt :)


I think the biggest problem you'll face is just the fact that you'll be welding 16ga butt welds with a MIG, stainless or not, in a small tube weldment. Your travel speed will have to be up there, and your fitup will have to be near perfect.

Definetely use .023" wire! ER308 for 304 tubing or ER347 for 321 tubing.

If you have a machine that has voltage and wire speed displays, I think I would start at around 13.5V and 135IPM. That's a wild guess, as I don't do much thin stuff with MIG.

You'll be looking to get a setting that obviously doesn't burn through, but that does produce 100% penetration. You'll also be looking for some color in the weld. Any welds that are flat grey, and you've lost all of the material's corrosion resistance, and have a very brittle weld. That condition on a header is a garunteed failure.

Unless you'll be using a spoolgun with a two stage trigger to post-flow the weld, the ends of each weld will turn flat grey. It's just a fact of life with MIG on stainless. (Also one reason that MIG on 4130N isn't recommended.) For the intermidiate stops along the weld, immediately brush the weld with a stainless steel wire brush used for nothing other than stainless, until the weld is silver. Do this while it's still hot! When you start your next weld, be sure to whip back onto the end of the previous weld, then continue regularly. This technique is kind of a band-aid, but in reality I've never had a failure doing it this way. To my knowledge, the city of San Fransisco's stainless drinking water filters that I welded are still doing fine.

Don't be surprised when the filler transfer sounds different than you're used to hearing. Stainless has a softer sound to it by nature, and I have a hunch that with the voltage/wire speed it will require, you'll be in what's called globular transfer. If that's the case, you'll see the end of the wire ball up and then drop into the weld.

08-30-2005, 08:51 PM
Any time. :)

shmoov69
09-07-2005, 07:52 PM
Mild is fine, stainless is better though. HPC (and others) makes a super high heat coating for the pipes that holds up to 2200*. I have had mine at egt's of over 1600* and the coating is just like new. I have also had the EGT's at 1480* from Dallas to Tulsa about the whole way on the PT 2 years ago. The timing slipped and I did not know it. Actually the balancer about came off too!
I went with mild almost 5 years ago because I did not have the extra jack laying around to do stainless. They are still great>(me knocks on wood!!).

RobM
09-07-2005, 09:34 PM
did you use any specific header kit for your turbo headers jimmy? im not looking to build turbo headers but i am looking to build some custom headers for a NA motor. I figure if the stuff you used is good enough for a turbo then it will be plenty for what i need.

PS: if you have any other pictures of your set up im very interested in seeing them as i am more fasinated with your build then any of the high dollar high glamor builds that ive seen.

shmoov69
09-08-2005, 07:30 PM
Thank you for the compliments! I do appreciate it. The "kit" is a box of 'U' bends that I got from Jeggs and the flanges from an old set of junk headers that I had laying around. A buddy of mine actually made them for me. My mind does not work that way! I don't think that I could start from nothing and end up with anything worth a crap! :rolleyes5
My main reasons for doing what I did with the car is that first, I had not seen any twin turbo'd street cars around at the time that I did it. Not saying that I was the first, but I had not seen any in the mags or anything like that other than a few of the mustang guys. Second, EVERYONE told me that a carb would not work, I must have fuel injection. Granted FI is much better, but carbys still work pretty dang good! Third, I had a goal to do it on the cheap (mainly because I had no dough to do it any other way!). Lots of used and junk parts to get it together and going. And surprising enough, the junk stuff lasted longer than the "good" stuff!.
PM me with Q's you got about my set up.