Use the process of elimination. If it has a diesel kinda sound, then that means whatever it is, all eight pretty much have to be involved. Right? Does it sound like ALL EIGHT of something? If it does, stop and think about it. What are the chances of all eight rod bearings knocking? The same amount? A rod knock is "about" the only other thing......with the exception of maybe wristpins that can produce that sound. Full floating wristpins is another thing that can do it. Do you remember if they are pressed or floating pins? With floating pins, you can get some noise from BOTH the pins AND the piston slap. It's like I said early on in this thread. A real HP engine with loose tolerances and floating pins is GONNA make some noise. Even pressed pin engines will make noise with real HP old school clearances.