Friday night driving the car around and I was coasting up to a stop sign, heard a noise like a belt squeal. I was damn sure it was a belt squeal but by instinct I looked at the oil pressure, ~50psi, plenty of fuel pressure so all good there. At the stop sign there was an intermittent squeak/squeal and I rolled out and down the road a bit till the squeal (still intermittent) lead to one slight tap.
Pulled over and popped the hood, there was a light, very intermittent tap coming from what seemed like the top end of the motor, decided to baby it back to the shop, during which I had no problems and no noise. Got to the stop and let the car idle for a few minutes with no noises whatsoever. Hm. next morning I idled the car for a bit and the tap had turned to a bit louder intermittent rattle which shook the engine, still sounding like it was coming from the top end of the engine. The exhaust sounded a bit too "poppy" as well, or at least so it seemed. The rattle very much reminded me of when a cylinder is misfiring and it throws the engine off a bit. Also with the slightly different exhaust it was making me think possibly a rocker had worked itself loose and there really was a cylinder not working right.
Yanked all the plugs, all was well. Pulled the valvecovers and all the rockers are fine. No debris in the valvetrain area, all seemed fine. Went ahead and rinsed the valvetrain with cleaner and drained the oil, front sump didn't show anything, rear sump however has a magnetic plug and I found this:
Ran a magnet through the oil I had drained, no debris. Poured the oil out of the filter over a magnet, no debris. Have yet to cut open the filter but I'm not sure if I'll get anything.
I have only put about 600mi on the car, had regular Valvoline oil in it for the time being. Was going to swap out for good synthetic at about the 1000mi mark.
What to do? Tear it down and go looking? Throw it back together with some good oil and see what happens? My thinking, if it's hurt I have to tear it down. If I hurt it more I have to tear it down. Blah!
Forgot to mention, was just cruising when it happened, hadn't dipped in the throttle at all. Car had been parked for a couple weeks as I was waiting on suspension parts and there was nothing wrong when I parked it.