Why did GM use cast iron headers on the GTO? Was it a noise issue? What does the Vette use? If the Vette uses tube headers, then how can both applications carry identical HP and torque ratings? Has anyone documented the performance gains with a switch to tube headers? Thanks!

The cast iron headers that are used on the LS motors are purported to perform nearly as well, if not AS well as a tube-type header. As far as why they used tube type on the new vettes is concerned, I can't answer the question. Typically, cast iron exhaust manifolds actually REDUCE the amount of head that gets disappated into the engine bay. Thin-walled tube headers give off tremendous amounts of heat....which is why many manufacturers "coat" them with thermal barriers and/or wrap them with something to insulate them.

True, and I imagine they had different limitations in terms of engine bay area, and sounds requirements to meet. I'm sure the performance between the two is near identicle, so they figured it wouldn't matter if they changed the casting material as long as it put out the same numbers.

i think it's mostly cost and sound. my headers gave me a large boost in power that was reflected in SOTP and track times

well ultimatley you might make a good point that a cast iron manifold absorbs heat simply cause its a large mass of the lowest metal in the world, but that doesn't justify the means. cast iron is used most likely cause its cheap and will get the job done, why are you going to spend so much money on better steel or even titanium for exhaust on a car that isn't the corvette? its a matter of cost effectiveness, the design is one thing a manifold could be just as good as a header, but material simply cause its cost effective

oh and there is a difference, i compared the manifold off the 6000 vortec of my cousins SS silverado to the exhaust manifold he stole off a corvette, no way similar