my lil 6.1 died at the 1000ft mark at the track

almost 6000rpm @100 mph
is it possible that my speedhut tach was showing less rpms than i actual had? So I over reved the engine? for what reason ever max rpm of the engine shown was 6000 on the tach. maybe it was over 7000 in real? I had the rv limiter set to 6800 previously and i sounded like i hit it but Tach showed just 6000. strange, isn't it? maybe the tach is inaccurate in lets say 10 to 15%.

That can make a rod bearing spin, right? That can make the oil film on the bearings get lost?

I am still searching for reasons.