coolant leak in header bolts

David Dickerson said

I have used multiple materials to try and seal those pesky end bolts. All have failed. Permatex recommended their pipe joint compound. That still weeps a brown goo. Was thinking of teflon tape with a combination of their high performance white thread sealing compound. I'm on my fourth try. Any thoughts?

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I had the same issue with my 340.
Cleaned threads twice with brake cleaner and a wire brush that is used for cleaning rifle bores, then I ran a tap down the holes.
Purchased new studs and sealed them with Permatex Ultra Gray, let them cure for two days.
Installed new nuts, never had an issue again.
Over 2000 miles and many heat cycles.