[bobcowan]

I beat on my car pretty hard, and this works pretty well for me:

No gaskets anywhere in the exhaust system. High temp silicone only.

SS Grade 8 (brand, not rating) header bolts. I gave up using the locking tabs a long time ago - too much of a pain to R&R. On some spots I use the cheaper black metal bolts that FFR supplied. I hand tighten to about *that* much. All bolts have a split lock washer on them. I check them every so often, but they never come loose.

Standard bolts and nuts on the side pipe flanges, standard flat washers. They happen to be a grade 8 (rating, not brand) fine thread. But that's only because I happen to have a box of them lying around I didn't know what to do with. I tighten them down good and they never come loose. They do look a bit rusty and discolored from the heat. Maybe the rust is a natural thread locker?

As the engine and exhaust warm up and cool down, they expand and contract at differant rates. Sometimes the joint is tight, and sometimes it is not; especially with metal gaskets like copper or alum. When the joint is not tight is when the nut will vibrate loose. This is the perfect spot for a split lock washer; they only work when the fastner comes loose a little bit, and allows the ends to spread out.

Put an internal star washer under the bolt head, a split lock washer under the nut, and no flat washers. TTYF. You might even try a locking nut with a internal star washer between them.

If they still come loose, the problem is not the fastner. The problem is the joint is not flat, and is allowed to rock.