By Nikolaj (130.161.173.58) on Tuesday, November 27, 2001 - 05:19 am:

I have this problem....
I wanna make my own header, and I have the place where I can bend the pipes. I just don't know about what the right material would be.. I have read about shops using a 304 stainless steel. A friend of mine uses 316/318 at his work which according to him is a better quality. But will this also be better for what I wanna use it for?? I can probably get that kind of steel cheaper through him...
Also, I don't understand why people use diameters that exceed that of the outlet ports. I wonder if they then have grinded the ports to match, otherwise it seems to me the flow of the exhaust is more important than the diameter..
My plan is to avoid any tight bends and to hopefully keep the whole thing within the car without shaving my crossmember underneath. That's the plan anyway...
So anyone got some steel knowledge for me??

By Tim Harding (Timh) (140.160.28.251) on Tuesday, November 27, 2001 - 12:54 pm:

There is a good reason for making the header tube diameter bigger than the exhaust port. This creates a "step" in the exhaust system. It helps prevent reversion of exhaust gas back into the combustion chamber. Theoretically you don't want any exhaust gas going back into the combustion chamber, because it dilutes the air/fuel mixture, resulting in a loss of power.

By Nikolaj (130.161.173.55) on Tuesday, December 04, 2001 - 09:51 am:

So what about materials?? I heard that the main problem with stainless steel is it's inablity to get rid of high temperatures...thus creating a much higher pressure which we are trying to avoid. I wonder if the higher grades of stainless steel have this problem even more. A guy told me the best thing would be plain steel, it only wears out on you....

By kelly (205.188.198.32) on Tuesday, December 04, 2001 - 01:22 pm:

from what ive read, keeping exhaust temps high keeps the velocity up too. thats why they sell header wraps. most headers today are either stainless or ceramic coated. maybe thats why. i know welding will have its own drawbacks because i heard stainless is harder to weld. anyways, just my thoughts...

kelly

By Lemke (63.62.205.10) on Tuesday, December 04, 2001 - 01:46 pm:

Stainless is much more expensive than mild steel, and mandrel bends are sometimes harder to find. Send me your email address, and I'll send you some pics of the header I built for my race car...