Originally posted by Jim2
Over and above what Ben said, the headers we use don't have sufficient expansion points to allow for material growth at operating temperatures. By comparison aviation exhaust systems have bellows or slip-joints at most multi tube unions or collectors. Our header tubes are welded to the collectors, and have minimal usage of expansion joints. Too many rigid mounting points as well.
From room temp to 1600F, 12" of stainless tube can grow upwards of 1/16" and is subject to continuious variations from 900F at idle to 1300F cruise, to 1600F on boost, so the header temps are changing constantly while driving, as a result they continously change shape to a minor degree, and if there are limited expansion points, they eventually develop cracks.
On a different note, some advertisments I read claim to have turbo headers made from "aviation grade 304 stainless". 304 is not (never) used for comercial aviation exhaust. I guess the statement helps sell product. Aviation is 321, it demands a price premium because thin wall 321 tube only seems to be used... in aviaiton exhausts.
That is why We only use 321 in our exhaust systems..
As to kevin Sorry just had no idea who you were and with the name kevin thrown out I had several people in mind but no knowing which one..
I am sure you have allot to offer on the topic.. Sorry don't go to rennlist much it typically is a mirror of what goes on here..