[RockSnake]

Thanks for all of the input. For the day in question, I was taking my wife for a "quiet" drive, and MIGHT have tagged 3000 rpm in one of my shifts. As to previous over-revs...that is a possibility, but I have a 5000 rpm rev-limiter in place.

Years ago, I worked auto-parts, and saw many bent pushrods...never a broken one. Hence my perplexity.

However, Mr. Mendez' comment causes me to think. I did experiment with extra advance on the timing...got a lot of pre-ignition, so I backed it off again. Maybe I did damage on that day that only showed yesterday. But then again, it was an exhaust valve (#4 cylinder), and I thought pinging usually hit the intakes.