Header install question ('17 ftspeed catted header)
 

Managed to get the old one out, though the little clips holding the O2 sensors weren't something I was ready for and I'm not sure confident they're going back in. Question is about the 'studs' (shown in pic) that connect the stock header to the rest of the exhaust. I got the nuts and gasket off but no idea how I'm supposed to get those threaded studs out to put them into the new header.

Any help is greatly appreciated.

You don't remove them, you leave them in there. Whatever overpipe you're attaching it to, you will need bolts and nuts to secure them together.

Lost me, that photo is of the stock header, not the overpipe. I'm keeping the overpipe/downpipe stock and just adding this header but it doesn't have any studs in it.

What am I missing?

Assuming I need to go get a pair of bolts and nuts, anyone know the specs on what's needed? Prefer not to guess (as I'm sure I'll guess wrong)

Found this in another thread, hoping someone can confirm:

Grade 8, M10 x 1.25 x 40mm bolts, and flange nuts (the ones with a wide base)

You're going to be attaching this header to the engine block on one end and the overpipe on the other end, you'll need two bolts for the header/overpipe connection. I am not entirely sure which bolts you need. This is what usually comes with the header:



https://www.tomeiusa.com/manuals/TB601-SB03.pdf

These will work.
In fact I keep a stash of these in a drawer.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

No issue with it being threaded all the way down?

None.
Look at the studs in the header from your own picture. They're threaded all the way down too (and into the flange).
Using a quality gasket is of more concern.

They're actually threaded at the ends, and where it sits in the manifold it's free of any threads. But if it's not an issue that works for me, planning to grab a new grimmspeed gasket as the one on there doesn't look like it's in great shape.

Went with these bolts as I didn't want to wait on Amazon or the parts stores that were out of stock but couldn't find a gasket to go from the header to the overpipe anywhere but the dealer and they closed early.....so guess it's not getting done tonight ��

https://subimods.com/products/subaru...o-exhaust-bolt

5/16 Bolts work too. I use a bolt that is just long enough to get full threads with a nut and use an all metal lock nut, sometimes called a "top lock." I have always had issues with the header to overpipe connection coming loose and a top lock fixed it.

So the matching nuts won't work? Should I loctite them? No idea where I'd get whatever sort of nuts you're talking about but given these were meant for a turbo manifold they'd hold up to the heat no problem.

They will, I just had issue with them backing off. Loctite won't work, gets too hot and it will break it down.

Dumb question but does the factory gasket between the header and the overpipe need to go one way or the other? Lost track of how the one I pulled out came off while I was trying to clean it. Seems it has a crush washer of sorts and want to get it right so I don't have to do it again. Thanks

*Edit: was able to line up the rusty side of the old gasket and figure it out.