Run a compression test

 

If you can get it to start, pull plug wires one at a time and see if the knock goes away.

 

ok.. dropped the y pipes and gonna have the cats checked (potentially just gonna cut them out as this rig is exempt from emmisions)... then dropped the oil pan and found a small piece of hard plastic in it, but that's not enough to make the noise, the pickup screen was clogged 99% with the RTV the previous owner used to seal the pan (what a mess), and pulled the bearing cap off the cyl. in ? and very slight wear on the bearing surface... not sure where to go now... i have a new oil pan gasket, so i'm gonna stop that slow leak, but since i didn't find anythin earth shattering, i'm back to square one with why it's not starting and what that knock was. possibly the cats burned up and are clogged to high heaven, but what were the chances both were clogged that much, i would think the engine would still run, albeit poorly, off one bank... oh by the way TomR, compression test was ok (done before i tore it apart further)