engine knock/rattle 360

It sounds like piston slap to me. That would happen when the machine shop returned a block with a bore that couldn't be brought back to round, but forgot to tag the block as such. Then the builder puts it back together. The sound might decrease a little after the piston warmup and expands, but the sound usually never goes completely away. I hope this is not what's going on with yours!

Other than that, it sure has a bad knocking sound. It truly is reminiscent of timing being way off from ideal. How did you ensure it was timed correctly? Did you try rotating the distributor while it was idling to see if the knocking goes away?

Good luck with this!