OEM Exhaust Manifold - type of metal?
 

Before the comedians come out of the dark, yes I know it's steel.

I know it's an odd question but does anyone know what type of steel? 400 grade, some version of stainless?

I had a collector installed to replace the cat and used aluminized steel that is often used for exhaust piping in other applications but it is corroding quickly which I think is due to dissimilar metal phenomenon and so to choose the a better type of tubing, I want to make sure I choose something that's copacetic with the type of steel the header is made of.

*comes out of the dark*

Vibranium if I remember correctly

It is typically a 400 grade stainless. I would at least use another grade of stainless to weld to it as well as a stainless filler, otherwise you are going to cause galvanic corrosion. Add some moisture to it as well and you have a corrosion cell. After welding spray it down with some citric acid, let it sit, then neutralize the acid and wash it off. Then spray with your favorite exhaust coating in a can.

i buy a lot of oem for myself and have had good results (https://www.subarupartsdeal.com/, got good deals and came quick). for you op, i think what you can do is go there, enter your vin and find the parts number. then you can google around. im sure you might find some more detailed info than hearsay. its helped me before when i needed to look up some exploded diagrams or assemblies when self installing.

I thought the manifold is cast iron.

Nope.

https://uploads.tapatalk-cdn.com/202...1415f52278.jpg


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Should've been, would really help the center of gravity. Whole exhaust should've been iron!!!

With some spikes/blades to slaughter everything in your path under there.

All I know is that those heat shields are sharp as all hell

It is already a form of header instead of the old school cast manifold.
This is one of the reasons that switching to another header doesn't get the same gains as you would see swapping out the stock cast manifold on a 1992 Civic.