How do hydraulic flat tappet lifters fail?

Righty Tighty said
Stupid question, but how do you watch the lifters during break in? I suppose I could leave the valve covers off, but at 2000-3000 RPM I would guess there'd be oil going everywhere. Or do you mean turning the engine over by hand and watching them before the initial start up? That technique was mentioned earlier and I like it, going to give that a shot.

There have been so many good tips in this thread, thanks everyone.:thumbsup:
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Yes, prime it turn motor by hand or even bump it (assembled) with no spark. You got so much assembly lube on it that a few revolutions wont hurt the cam or bearings. Remote starter switch is great for this. The lifters are very easy to see with no intake on it. Hand rotating will be enough to notice if the lifters are 'rolling' in their bores.