LS2 with "slight low end knock"
 

Need some quick advice, I am looking at buy an LS2 from a guy who said it had a slight knock in the low end.

What are the best and worst case scenarios here?

Is there any way to check the motor without going through too much trouble? It is currently a complete LS2 out of a 2005 Corvette with all the accessories and everything still on it.

That is tough without the engine in the car. Turn the engine over with a breaker bar or ratchet, listen for any noise or rough resistance. You could pull the plugs to check their condition, pull valve covers too. If you can't pull the valve covers check the bottom of the oil cap for burned oil residue burned smells or milkshake looking crap.. Those could be indication of further damage, or neglect.

If it is a low end knock it could be as easy as a simple rebuild with new bearings, rings, and minor machine work. At worst it could need all new bottom end components.

The knock could also be some other misdiagnosed noise.

I bought my LS1 with a rod knock as well. It also had some rust in the bores and would not turn over 360 degrees. It needed a crank, rods, pistons, and a bore of .007".

Good call, I am taking a fellow V8 FD owner with me for insight. I will also plan to bring my bag of tools and check everything I can prior to handing over the cash and loading it up.

Do you mean the bottom of the engine or at the low end of the RPM range?

There is a reason he/she is selling the motor... a "knock" generally leads to a bunch of work... you are basically getting a block with a matched set of heads... and a valvetrain. Expect to replace the crank, pistons, rods, and all bearings.... and you (if really unlucky) may have more problems than that. Aluminum blocks are lighter but at a cost of strength... look very closely at that motor. Or have really deep pockets.