How do hydraulic flat tappet lifters fail?

I hope not, but best believe I'll be inspecting all of the guides, bores, rockers.....EVERYTHING.

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:
The best way to check for rotating lifters is by thr push rods mark them with a paint marker and with the valve cover off or one with a whole cut in it see if the mark spins