[Jim Vander Wal]

Tightening those bolts was a regular maintenance item for me. Didn't matter if I ran 5/16-18 or 5/16-24, all Grade 8 hex head, not sockets. I'd tighten about as much as I could but they'd still loosen up.

Part of the problem is the gaskets, if used. The more typical exhaust gaskets would burn out and then the flanges would be loose. I also built .060" solid copper, these could be tightened but the bolts would still vibrate loose.

Vibration is most of the problem, or that's what I believe. Double nuts can help, split lock washers may help. I was never a fan of the distorted nuts as previously mentioned, but these should hold and are probably the best solution.

I never used Anti-Seize on the flange bolts, never had a problem getting them off. May not be the case for your install. I wanted them to stick, the Anti-Seize seemed counter productive. Did always use Anti-Seize with steel studs into the aluminum heads but didn't have as much trouble there and easier to get to.

Jim