Just quickly, would 304 stainless schedule 30 weld els be suitable for an exhaust manifold? And does anyone know where I could get a flange made up or one that's already available?

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ST205

304 isn't the best... 321 should be better

I think I have a 304 flange in the garage if it's of any use?

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Kris
95 ST205 - slept for 10 years, now waking up...
Avensis
http://www.gtfours.co.uk
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Turbocharging - the replacement for displacement

I think I will do one in mild steel first, a template. 321 stainless is expensive and difficult to obtain. Would be slightly annoyed if I buggered it up. The flange might be of use though, how much do you want for it?

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ST205

Looks like 321 stainless is nearly impossible to find, 304 might be the only choice. Hopefully a sched 40 304 pipe should be strong enough. Easier to weld too.
316 is a option if that's better?

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ST205

You probably won't find weld els in 321, it's meant for very high temperature applications rather than steam pipe that weld els are intended for.

321 pipe and elbows should be readily available from metal suppliers, but it is expensive due to it's less common, more specialist use, and the addition of Ti (which provides it with much better thermal cycle performance than the more common alloys).

304/316 will crack fairly quickly, especially with the weight of a turbo dangling off it, or if you restrain it from expanding along the pipes length. You might just be better off sticking with a mild steel and accepting it will surface rust.

Will check the garage to make sure I have the flange - I don't want anything for it

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Kris
95 ST205 - slept for 10 years, now waking up...
Avensis
http://www.gtfours.co.uk
_______________________________________
Turbocharging - the replacement for displacement

Well mild steel would be a whole bunch easier, and cheaper. Can it be normally mig welded or do I need special wire? There's plenty of VHT paint I could paint it with.

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ST205

Yeah plain normal MIG wire will be fine.

What's the best size piping to go for, 2"?

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ST205

No, try to make it about the same size as the standard runners (unless you are building a massively powerful engine?). You want to keep runner area down to keep velocity up.

what is the standard ID of the exhaust runners?

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ST205

Don't remember mate, I've been out of this game too long! I do remember that they're oval, not circular and vary depending on the cylinder they go to due to the exit angles from the head. When I was looking at making my own exhaust manifold I seem to recall 38mm rang a bell.