I have recently removed the head of the saff to replace the head gasket.
I was aiming to replace the nuts when i refit the manifolds, as the ones i have taken off are worn and slightly rounded, and i dont want to have a problem removing them in the future.

My question is, is there a specific type of nut i should be using? the ones removed have some small slots in them. I can pick up some stainless steel or normal mild steel ones from work..

Cheers.