I am in the tedious process of designing a twin-turbo 406 setup and am in need of some info. What is the best material to use on the headers for a turbo system ? This will be on an extreme performance street machine, not a pure race car. It won't necessarily be a daily driver, but I would like it to behave like one.
At first I was only considering stainless steel, but a guy from Cartech told me today that stainless steel has a high expansion rate and is prone to cracking on street vehicles. He suggested 14 ga. mild steel with a professionally applied high temp coating. Since I am not a metalurgist, I really need some help here. If stainless steel is better, what kind (i.e 304, 321, etc.) and why ?? Is the mild steel a better approach ?? What are advantages & disadvantages of each ??

 

I talked with George @ turbo Technology today & he thinks that SS is the only way to go & they use 321 SS.

I bet that GMIFast, would have some input as they make turbo headers all day long.

BW

------------------
Bob Wooten
71 Camaro, 91 EFI
r71chevy@earthlink.net
www.r71camaro.homestead.com

 

Stainless does have a significantly higher expansion rate than mild steel, but so what?!! As long as you design the headers with this expansion in mind (i.e. no log style manifolds, keep expansion directions and pipe lengths similar so it doesn't attempt to tear itself apart when heated), you will have no problem.

304SS is the cheaper kind of SS and will not corrode as quickly as mild steel. I believe it is a little easier to weld as well. 321 stainless is generally regarded as the best SS to use for turbo headers (it withstands higher temperatures better than 304). There's always Inconel, but thats just for super high temp applications like Indy

It also depends on your budget. If you're going all out and having someone make the headers, I'd spring the extra few hundred for 321 or 304, but if you're fabbing it yourself and only need it to last 2 years, try the first time in mild so you don't destroy a few hundred dollars of mandrel bends learning.

If you need more information on material properties or design, feel free to post. I've got a ton of resources here at work.

Andris, resident engineer

------------------
Andris Skulte
Skulte Performance Designs
Z28tt-89 IROC T56 DFI Twin Turbo
http://www.skulte.com


[This message has been edited by askulte (edited April 10, 2001).]

 

Stainless Steel is the only way to go...i know it sucks, but you gotta pay to play.

if you want the headers to last a while...spend the extra $500 and go with 321SS instead of 304SS

 

For 98% of the turbosystems on the street/strip, 304-SS is perfectly suited. Do NOT use mild steel.

 

GMI,

are there expansion differences between the two SS's? is the 304 easier to weld?

BW

------------------
Bob Wooten
71 Camaro, 91 EFI
r71chevy@earthlink.net
www.r71camaro.homestead.com

 

Honestly, I am by no means an expert on metallurgy. I do not remember what makes 321 a "better" material. I do know that it is much more expensive than other grades. Really unnecessary for any headers, according to my boss. I will ask him why when I get a chance, boys.

 

Wow - this is exactly the kind of info I am looking for. I don't have a problem spending the money on doing this correctly the first time. My biggest obstacle now is deciding whether to fab this up myself vs. taking the car to a shop. There are shops that are capable of doing this work, but they are all quite a distance from where I live. GMI Fast - please let us know what your boss says about the differences between the 304 & 321. Also, do you use stainless on the flanges at the cylinder head ?? Does the high expansion rate of the stainless cause problems with exhaust leaks ?? Thanks for all the help.

 

I guess I'll be quiet now

Like I mentioned before, 321 withstands higher temps than 304.

Andris, having a bad morning at work

 

wish i had $2000 to spend on custom turbo headers

 

I don't know if it helps to know but every part of the exhaust in a TTA is stainless,no problems with any sort of cracking or leaks.

Steve

------------------
TTA#124-129,bone stock.Cloth/T-Top Festival car
TTA#850,bone stock,best 13.68@100
TTA#861(almost sold),near stock,best 11.99@112.26
TGTA#01,nowhere near stock,9's or bust
Pics and info on My Cars
TTA850@TurboBuicks.com

 

Also,whats the deal with wanting to do twin turbo's?Just curious because it seems like alot more work than a single along with more money and there are turbo's out there that can flow more than enough air as a single than most people would ever need,the PT-88-TSE comes to mine and flows enough as a single to make 1200hp.Just a thought.

 

Well, in a "street" car, twin turbos benefit from sharing the airflow requirements. The time to reach full boost is shorter (lag) than a single turbo capable of the same airflow. In a "race" car, while there are single turbos that can support over 1500hp, they are being worked VERY hard. The big dogs run twins to push over 2000hp and take a load off the turbos' task.

------------------
1989 T/A, 400" CNC Bow-Tie tall-deck, JE 8.5:1 pistons, Scat H-beam 6" rods, Scat 4340 crank, Crower roller cam, AFR heads, Tiffin Racing sheetmetal intake, Holley 75mm t/b, DFI, variable injector controller, 72# inj., S/X fuel system, Hahn Racecraft T76 single turbosystem, NOS 150-hp dry fogger, TH400 w/GV overdrive, Dana 44 w/3.70's, Baer Track brakes, Simmons FR 18X9 and 18X10 wheels, P265 and P285/35ZR18 Nittos, Spohn suspension, Eibach Pro-Kit springs, KYB AGX shocks/struts, Corbeau Targa RS seats, TeamTech 5-point harnesses, Sparco steering wheel, MacEwen white gauge overlays, Phantom gauges/tach, B&M Pro Stick w/carbon-fiber ****, REAL carbon-fiber dash/console kit (don't ask), S&W 8-point rollbar, Lonza aluminum pedal covers, Pioneer/Boston Acoustics stereo system, filled side markers, Audi clear fender marker lights, custom clear front turn signals, custom clear taillights, IMSA-style cowl hood (don't ask), custom medium Intense Blue pearl paint, tinted glass. Whew!

Best ET w/383" S-trim: 10.796 @ 125.8 mph
Best ET w/400" turbo, nitrous: Summer 2001

Member of Midwest F-Body Association www.mfba.org