Originally posted by 911rudy
I asked the question before on the Renn forum if there was any data on the cracks in headers on turbo bracket supported headers/turbos and the non supported ones. I am talking about the turbo bracket that a lot of people leave off when they replace their turbos. I know I had to cut and reweld mine when I went to a K27 but I still put it back on. I don't think that the two straps around the muf are enough to stabilize the turbo and headers but there doesen't seem to be any data on it.
I made a deliberate decision to not use the support bracket as you mentioned. This was with B & B headers and a fabricated muffler, a bullet type can with a turnout. There was no muffler support bracket of any type either. I never had any issues with cracks or failures related to the eccentric load of the muffler, or the load of the turbo itself, in 5 years of extremely hard track use on two sets of headers. Of course my experience may not be the rule. The weight of the muffler assembly is probably a big factor.
My thought process was that unless the bracket fitment was extremely precise, the bracket would actually be introducing stresses into the header assembly that weren't present to begin with, potentially contributing to the genesis of fractures. In addition, a bracket bolted to the crossmember from the turbo will not allow any movement that may be wanted by the header assembly as it grows and shrinks with heating and cooling.
This is not to say that cracks did not develop, as all B & B and GHL headers will crack eventually, usually in the welds or proximal to the welds in the collector area. Regular maintenence of removing the system on a semi-annual to annual basis depending upon severity of use is critical to prevent gross failures and foreign object damage (FOD) to the compressor wheel through repair of small developing cracks. Many times these cracks aren't readily visible while the headers are cool to the touch, but when the material is very carefully heated to a simulated operating temperature the appearance of small cracks is enhanced, aiding prophylactic weld repairs, not to mention you can see the spiders web appearance on the tubing itself which is quite dramatic.
Others have used/considered using coating processes, I assume to manage thermal issues or for aesthetic reasons, but I would strenuously recommend against this as there is no way to debride the base material sufficiently of the coating media in order to be able to make a functionally sound weld repair when the time comes.
Lastly, many people don't recognize that these headers are actually a consumable item, and should be replaced on an given interval depending upon use. It's not unreasonable to expect to install a new set of headers every other season, if the car is a dedicated race or track day car and sees more than a few events per season.