lan evo,
Check the crank pulley for freeplay. You can pry it with a bar. There should be NO movement at all, but if there is, measure the amount of movement with a vernier caliper. Acceptable tolerance is 0.25mm.
gooseman,
The beginnings of a spun bearing sound a lot like stuck lifters, only that it resonates from lower in the bay. If you have a loud exhaust or play your music loud, this is easy to miss.
If you catch the knocking early, you may get away with just a new set of bearings and remachining your crankshaft. If you catch it later, you may still get away with a new crankshaft. If you don't catch it at all, you get to drop in another engine.