| in the alloy to do just what you are saying, but was unaware of an "H" specification for this alloy. Perhaps I'll see if I can find some and keep that in mind for the next set when these fail. At the moment, I am sitting on the fence about these flanges as you pointed out. To my knowledge, most manifolds out there also use mild steel for the flange. Why this is I dont exactly know though. I still have opportunity to get some flanges made in 321, but who knows what the price of a piece like that will cost! One thing I have been thinking about is the fact that the longer runner from the frontal cylinder is going to expand quite a bit more than the other two runners. They are all collecting together at the back and the front two cylinders are arching over to the junction. I'm afraid that the expansion from the two frontal cylinders is going to leverage the collector area and tend to make it want to fail there. So what I am going to do is cut the head flange between each exhaust port to allow the flange to float. The design of the stock head gasket is such that it will alow for some creep of the flange and not fall apart. The idea here is to figure out what kind of torque I should put on these flange nuts so as to allow the manifold to seal to the head, but also to allow it enough slack to float a bit. I dont know how well this theory will pan out, but after considering the expansion of the metal, I am certainly not going to leave the head flange all one piece, at least... I think this is the #1 reason why manifolds fail - all that internal stress of expansion and no slack in the design to allow for it, then you develop cracks right at the welds to the flange itself... I know, in many ways, that I am re-inventing a bunch of wheels here, but there is so little information out there about manifold construction as everyone just wants to tell you how good they perform and want your CC#. No one gets into these nitty-gritty details, at least on a webpage but I am sure there are some good books out there that cover all of this plus the things I haven't considered...
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[ agpowers@bellsouth.net ] Enthusiasts soon understand each other. --W. Irving.
Are you an enthusiast? If you are out to describe the truth, leave elegance to the tailor.
Albert Einstein
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