Planning to make a header...

[saltrunner]

I want to make a set of turbo headers for my car but I have one major question. The flange that bolts to the heads has oval shaped ports, how do I get he runners to fit in the header flange? Do I squash it or press the tubing over a die to form it?

I plan to use 321 SS for the tubing, what would be the best material for the flanges on each end.

Here is an example of a header for my car but for a different turbo.

[Blown S-10]

i think i would make a die. then carefully hammer it. don't know if that would work on ss though.

what is that for, a 3.8 GN ?

[saltrunner]

So I could cut say a 2" section and press over a die to make the transition, then weld my runners to that? 321 SS is formable but it will work harden, do you think it will need to be annealed?

I have also heard where it is better to weld the tube to the flange on the inside and port out rather than weld the tube to the outside. Do you think there is any merit in that statement?

It is for a 3.0L mitsubishi 3000gt vr-4.

[Blown S-10]

i don't work with stainless. nore can i see how much the port is ovaled. but, i think a pretty sure way to do it would be = cut a pie slice shaped section where the oval flats are. then shape this down to where they meet. and weld the seem. but i think a proper die pressed into the pipe would shape it well also.

i always see the pipes welded inside the flange. and have "heard" that doing it this way is preferd because it somehow reduces stress on the pipe. i don't know.

[saltrunner]

More pictures, these are the stock manifolds

http://www.stealth316.com/2-exhmans.htm

[Blown S-10]

thats a much more of an oval than i thought. hmmmm. can stainless be heated and shaped like mild ? if so, i think i would make a spreader for that, and heat while screwing the spreader.

you can't buy ends like that ?

[2gofaster]

Generally, I'll put the tube in a vice and oval it til it'll fit into the flange opening. I'll insert it in the opening til it's about 1/8-3/32 from the other side and then make a 1/2" weld along the two sides that touch(in this case, your top and bottom. Then I use an air hammer to stretch the heated metal out to the corners. On the inside, I won't weld all the way around the inside of the flange. I'll do 1/4-1/2" welds around. Then I'll weld the outside with silicon/bronze filler where the tube is inserted into the flange. I'm told the silicon bronze draws the heat out of the exhaust port as also dampens the "ring" you get with tubular stainless headers. I'll see if I can find some pictures of the turbo headers I did for the Ford 4.6 32v motor which has a very similar port shape.

[saltrunner]

Thanks for the input guys! I am going to get some laser cut flanges and try this out of mild steel first and then make a jig off that.