I have to put it on a tach tomorrow, & check the timing...be surprised if I find anything.
It sounds like a mellow valve knock when I blip the throttle hard. I hear it coming from the motor, from under the hood when I'm hand-throttling it. Car does NOT knock under load...or at least, it can't be heard from the passenger compartment. It made the same noise after I adjusted the valves (they were quite loose). I've never had a slant 6, so I don't know if it's normal (I doubt it :/ )
Flex plate? I can check that by pulling the dust cover & rotating the assembly, correct?