I'm learning to weld with a goal of making my own header, but I need flanges made. Any place that is familiar with this already? Any special details to put in my model I give them?

 

First, it depends on the head.

Second, google 'diy header flange xxxx head'

There are a few places that make them, I just can't think of them off the top of my head.

 

Oh, I forgot to include a big point in my original question.. Best way to match up pipe to oval ports? Is everyone just going to say vise?

The head is too obscure, 12 valve honda stuff.

 

Do you have pictures of the existing exhaust manifold?

This might get expensive if you don’t have access to a machine shop.

What I would do is take an exhaust gasket and the head and original manifold down to a fabrication shop.

The gasket will give a reference to what a bare flange should look like.

Replicate the exhaust manifold flange out of 1/4” stainless.

as far as the runners, you’d make one end of the primaries oval by use if an expanding die set. I guess you can expand it and the crush it oval, but again, I’d talk to a fab shop and see what ideas or tools they might have to help with this. You can always start slitting the pipe to relieve it and weld it all back together whence you have your final dimensions correct. Maybe Burns Stainless might have a solution for you.

once you have the primaries on, the other end is round so it’s just slipping and fitting and welding it all together. Another flange for the merge collector and you’re done.

you will definitely want a 4-2-1 header on that small of an engine.

Are there any off the shelf headers that exist for the engine (I doubt it but a shot in the dark is still a shot.)

 

Is it possible this fits your head?
https://www.ebay.com/itm/202173754814

 

Ya, there used to be DC and Pacesetter 4-2-1, but they are like finding unicorns now. Those were also only 1 3/8 primaries, I'd like to build a 1.5 or 1 5/8 primary to duplicate the DC 4-2-1 LS header.
That OBX is 4-1 chinese junk that hangs way under the oil pan.

I have one of these heads that is ported as well, and was thinking of shaping a chunk of steel into the port shape with a slight cone and hammering it into the pipe end, but.. I dunno. I was already also looking at expanders to slip fit the ends a little for (hopefully) easier welding as a noob, rather than butted up welding.

 

If that header fits your head, buy it and chop it up. The primaries are already welded onto the flange, that'll solve two problems.

With a custom design flange you have to think about the labor that goes into programming and lasering out the part. Plus the cost of the materials. Since this is likely to be a one-off part costs will be higher.
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Maybe ​​​​​​@850Fabrication can give you an estimate on a custom flange.
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Can you do the CAD work yourself? If so, that may save you some $. There are lots of laser and plasma job shops out there on the internet and probably locally to you as well. If you can draw it up and just send the shop a .dxf (assuming you're only looking for a 2D part cutout), you basically just pay for the material and machine time.

 

CNC Plasma here.

Shouldn't be an issue to send in a DXF. Just be sure that the circles are actually circles and not a polygon. Some CAM software treats circles differently than polygons. Sketchup likes to export circles as polygons so just be aware if that is your CAD package. Also note what unit of measure the DXF is exported as.

And finally, make sure your CAD file is dead on, what you feed into the CNC machine is what you get out. Assuming the owner of the machine has it dialed in correctly.

One more thing, if you are doing a 3 piece flange export each unique piece as a separate DXF. Makes nesting much easier.

 

I might be able to help you with flanges. I can CNC Plasma them but I'm getting more comfortable with the mill

I just made this (one my first real parts off the mill)
https://www.ebay.com/itm/Tig-welding...4AAOSwWkRfnKPr

 

Nice!