Engine Exhaust Bolts
 

I removed rusted steel exhaust bolts and nuts from my stainless steel exhaust system (manifold, flange).
Is there a certain grade of steel bolt I should replace these bolts and nuts with or can i use stainless? Why would the factory use straight steel on a stainless system?

+1 same question

Because the bolts are "consumables" like wheel bolts and rotors. i'd suggest grade 8 bolts at bare minimum.

The best bolts I have used are the Porsche manifold to cyl head bolts. With a little Anti-seize on the threads they last indefinitely. Best quality bronze or SS nut & washer & you are set. I ordered ARP SS bolts but they are only available in slightly too short or slightly too long. Also ordered Suncoast install kit from the website thinking I would get OE fasteners, but it is average quality, overpriced aftermarket hardware. Due to the Hi-temps & constant heating & cooling you don't want grade 8 or above fasteners since they are too brittle. Most SS fasteners you find are not strong enough. You really want hardware designed for exhaust duty.

Does anyone have a good source for these high temp exhaust nuts and bolts?

I had a second look at the manifold bolts and the heads look ok, rusted head but can be cleaned, the threads look ok so I'll reuse them with some antisieze that is aluminum friendly.
The exhaust flange bolts and nuts were wasted so I'll need to replace them.