Cracked DS header

[DCVING 6]

I think I have a cracked drivers side header. I hear a fluttering/ticking noise under accelaration. I only have 10" of vaccum while ideling in Park. Are there any problem areas on the drivers side I should focus on?

I know it needs to be welded up. Where should I go for this? Is it worth it to get them powdercoated after its welded up? Does this prolong the life?

 

[DCVING 6]

Oh yea, forgot to add...

 

[turbosam6]

Take it to a local machine shop, or someone who can weld stainless. Its a specific grade, but I don't remember what. Anyway, make sure that the header is bolted to a head or something, so it wont warp from the heat. I don't think you mean powdercoating, probably jet hot coated or something like it. Not sure on that one, if it helps or not. Do a search, and you can find info on adding braces to prevent future cracks. Good luck.

 

[salvageV6]

I put a welded one on today on the GN along with the Mease downpipe.

I painted mine with VHT silver paint and cured it in an oven at work at 250 and 400 F for a couple of hours.

I doubt it will hold up but it looks purty now.

If they weld it make sure it is bolted to a heatsink piece of iron or else an old Buick head to insure the flange stays flat.

No more tic tic tic for me.

 

[Tom Tom Turbo]

It usually cracks between the first 2 tubes. I had a local Super Gas drag racer weld mine, plus he flattened the face, and it fits better than it did before and far better than the pass. side. Be sure that they don't get weld spray in the tubes or atleast make them clean it out! Good luck!

 

[tom h]

the stock headers are 409 grade stainless -- a crappy "automotive" ferritic stainless.

Using 309 filler rod is supposed to make for a more ductile weld, meaning it "may" be less likely to crack again.

 

[DCVING 6]

So whats the deal then, have em fixed?
What is an average figure of having a pair welded up?
Is it worth it just to get aftermarkets?

 

[Chyke]

409 Stainless

Ok lets start off by clearing one thing up. 409 SS is not some crappy ferric automotive stainless. Buick put thought into the use of this material for the exhaust on these cars. 409 is actually perfect for it's intended use. It has the ability to experience vast thermal cycles with little or no detrimental effect on it's metalugic properties. It also posses a number of other desired properties, look them up. The reason for the common cracking of the drivers side header is actually the design of the header itself. The feed and log design is extremly poor, it creates areas (where the feed meets the log) of high thermal stress. Hence the cracks. If you look at ATRs design of the replacement header you can see how all the primary tubes terminate at the collector. This way all exhaust pulses and heat remain semi-eqiuvalent. If the factory headers where made out of the more common 304, and utilized the same design, everyone would have big time issues. Obviously 321L or 347L would be the material of choice but is cost prohibative. Just my free 2 cents.. Take the header off and have it welded. Ensure the correct rod is used. Oh and one more thing, 309 rod is technically used to weld metals of differing properties together. (304 to 409 etc.)

 

[UNGN]

Actually 409 is a ferritic stainess, if it wasn't, it wouldn't rust like it does. Iron containing 400 series stainless materials are much cheaper than 300 series non iron rich stainless materials. That's why they are used instead of 304.

The design is poor, but corrosion in the heat affected zone is a major contributor to crack propogation. Corrosion due to the fact there is iron in the alloy. Using ATR's header design as a good example is funny because ATR headers are known to crack, too.

The best way to repair this is to rout the crack out and have it TIG welded using stainless rod while bolted solidly to a head. $40-50 dollars is a good price to pay to have this done.

 

[Chyke]

OK.....

Obviously you missed the point. So there is no need for me to elaborate. I never said ATRs headers were good or bad, only providing a visualization that most semi-intelligent people can relate too. It never ceases to amaze me how often truly unknowledgeable people attempt to validate their existence through bull**** banter relating to SOME knowledge about nothing. Please go back to bed would ya... My point was that Buick choose the metal for a reason. The fact that it is considered a ferric stainless was not the point. It has quite good "longevity" for production vehicles versus the cost to manufacture. Please read what someone is saying in the future and refrain from commenting for no reason. Just having one of those days

 

[tom h]

Re: 409 Stainless

Originally posted by Chyke
... 409 SS is not some crappy ferric automotive stainless. Buick put thought into the use of this material for the exhaust on these cars. 409 is actually perfect for it's intended use. It has the ability to experience vast thermal cycles with little or no detrimental effect on it's metalugic properties. It also posses a number of other desired properties, look them up. .... Ensure the correct rod is used. Oh and one more thing, 309 rod is technically used to weld metals of differing properties together. (304 to 409 etc.)

Another source of info at: http://www.atlas-steels.com.au/techinfo/index.html , this is the section on FERRITIC stainlesses. Click on the "409" icon for the data sheet.

409 is a titanium stabilised ferritic stainless steel.
Although regarded as a general-purpose chromium
stainless steel the primary application for Grade 409
is automotive exhaust systems. ...
A light surface rust will form
in most atmospheres; this rust retards further corrosion
but makes the surface undesirable for decorative applications.

Generally 409 is classified as resistant to scaling in
intermittent service up to 815°C [= 1500ºF] and up to 675°C [=1250ºF] in continuous service, but these temperatures are
dependent upon the exact service environment.

Readily welded but a pre-heat of 150-260°C is
recommended. Grade 409 or Grade 430 electrode or
filler rods can be used, but AS 1554.6 pre-qualifies
welding of 409 with Grade 309 rods or electrodes.
These austenitic fillers result in a more ductile weld. [meaning, less likely to crack again]

Possible Alternative Grades

304: Better corrosion resistance and heat resistance but at higher cost.

321: Higher heat resistance than 409 or 304.

Aluminised steel : Lower resistance to exhaust gases, but at lower cost than stainless steel grade 409.

I also agree that the "log" design probably contributes to the cracking. They tried to mimize the effect with the rolled convolutions to take up some of the mechanical stresses.

In order of preference, 321 is better than 304 is better than 409.

321 is 3 times higher material cost than 304.

More interesting reading at
http://www.burnsstainless.com/index.htm

Ultimately it's going to also depend a lot (or mostly?) on welder skill and what he will stand behind.