Exact same thing happened to me, TWICE! On the second build, I used a zinc additive with the engine oil, but that didn't help either. After 2-300 miles came the knock-knock...I'm hoping its just a string of bad luck and not something I have been doing because ill really kick myself in the but if it could have been prevented . Twice ...
They don't like the bottom end touched without machining everything before it's put back together.