I thought that I would post up my version of the weld el mani.
This is for my 99 Miata DIY turbo project. Elbows are stainless from Ace Stainless and flanges from Weirtech.
I didn't want to do the usual "two 90's into two tees" as the flow from cylinder one just bashes into the flow from four at the outlet, so I used six 90* elbows.
I started with four elbows tacked into two pair. I cut an angle at the bottom (about 3/8" off of the inside edge) that would allow the two to come together enough that the exit matched up with the outlet flange.
Afte that, it was a matter of grafting the #2 and #3 elbows into the outer runners. This was all done by trial and error fit. After I got the tubes to fit, I marked out the placement of the runner onto the outer tubes and drilled two 3/4" holes and then opened the rest up with a die grinder and a carbide burr.
The head flange ends were ovaled to match the outlet ports in a vise.
After that, it was a matter of blending, deburring and prepping to weld on the flanges.
Head flange was then welded on. 309L filler rod was used to weld the stainless to the mild steel flanges.
After the head flange was welded on, I was able to square up the outlet end and then weld on the outlet flange.
Here are a couple of shots after welding on the flange. I did not backpurge the mani when I welded on the flanges, so an occasional hickey on the inside. Here it is before any dressing of the inside welds.
After it was finish welded, I polished it up with different wire wheels in my die grinder. It came out pretty good. I had about .040" out of flatness on the flange, so I took it to work and had a guy flycut the flanges so that they were flat and parallel.
All in, I have $63 in the manifold. I have just finished the turbo install and have been working on tuning the car.
The mani has held up fine so far. I am the first in the US using the Adaptronic ECU in an NB Miata, so it was a bit of a learning curve, plus there were no good maps out there other than a generic super conservative map.