[ByronRACE]

It's very difficult to break a ford V8 by running it lean.

That is, unless it begins to detonate.

So, did it run lean ONLY...and cause thermal damage like melted pistons (near impossible to achieve, the engine won't hardly run at that lean air/fuel ratio), or did it rattle and you didn't hear it and/or didn't back out of it and holed/broke pistons. If you have broken rings, lands, and associated damage...it detonated.

Detonation is usually caused by excessive spark advance. Yes, a lean mixture can influence it...but it's a lesser influence. A properly timed engine can tolerate a very lean mixture; even at wide-open throttle...unless this is some exotic high-compression thing.

Byron