Turbo headers: mild steel or stainless

[BigBlockOlds]

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]

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]

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]

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]

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]

can you mig weld a set of turbo headres? or is that not recomended? i'm going to build mine with 321 also.

[Supra510]

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:


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]

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.

[Matt@RFR]

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]

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:


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]

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.




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

[jakespeeds]

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]

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]

why'd you put the thermal wrap on the compressor outlet???

[Supra510]

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]

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]

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]

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]

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]

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...