when making a turbo manifold i have been told to use "steam pipe"

with steam pipe i understand it is mild steel and can be acquired with wall thickness's of 3mm to 3.5mm which would be optimum for a turbo manifold.
i have also been told to use a diameter of about 1-3/4" to 1-7/8"

does this sound right to those that have done this before??

also would steam pipe that has been galvinised matter??? it will just burn off anyway wont it and its cheaper..???
does it matter if the pipe is seem welded??? will this crack or should it be ok??? this question is pretty important i think...
what have people used to coat their manifolds after making them...? high temp. paint... HPC coatings and what were the results...???

any help will be greatly appreciated (oh and i have already read through most of the threads that have this in them thats why i have specific questions on the seem welding etc.)
cheers

no need to go any bigger than 1 1/4' diameter.

Yep 1 1/4 inside dia is all you need.. Let the gasses expand in turbo... Your thinking n/a manifolds..
Too big and it effects spool time and too hard to merge pipes on collector creates under bonnet heat etc... The steam pipe will be champhered so weld will almost be level, a small gap 2 or 3 mill hepls aslo.... Either mig / tig weld..

thanks guys...
TIG welder will be the weapon of choice.
1 1/4" sounds good i will get shopping i think...
cheers

The pipe size for the runners should be 32nb. I don't recomend getting galvanised ones because unless you clean it off it will tend to weaken the weld. All the bends are cast. The lenghts come as either seam or seamless, it won't make a difference unless you're chasing rediculous power.

excuse my lack of knowledge but what is 32nb ???
is that 32mm diameter???
thanks for all the info guys anymore advice is more than welcome
cheers

nb stands for nominal bore

thanks for that.... gotta get around to ordering bits...
cheers

Just a quick one.
Has anyone made a stainless manifold?
If so what wall thickness did you use and
What grade of st/st did you use?

ive heard that the stainless ones sometimes have problems with cracking etc due to the thinner wall thickness...???
cheers