List Wisdom needed knocking sound

[kcope]

I went for a drive got home and parked the car. Later on I started it and heard a BAD knocking noise like a rod bearing. I put it away and had my brother in law listen with a stethoscope when i started it. he said it sounded like the knocking wasn't comeing from the case but higher up and on the drivers side.
After about 3 weeks I was able to get the car towed to the shop and guess what. No knock. he test drove it a couple of times and I rode with him on a test drive and the car ran exactly like it always did!
the only thing my mechanic could think of was that maybe some thing like a small nut got sucked into the cylinder and disintigrated. the car runs like a top now. I can't figure it out.
I had a car with a bad bearing and this noise is just like what I remember. the shop is going to change the oil and checkfor metal in the case and filter. but thats all we could think of to check. Anyone have any ideas? TIA

[slater]

Not sure what it would be, but I doubt it would have been a nut. That would have done more damage and most likely bent a valve or something (ask me how I know!).

[kcope]

I can't believe that myself. Maybe the car healed lol. When they check the oil I'll know a little more.

[H.G.P.]

Reminds me of years ago on a Buick, I had a "knock". Took it to the dealer, and they found hardly any oil in the crankcase! (I think either the drain plug was not sealing, or I needed a new oil pan gasket.)

[Westy]

Carbon piece. Even the littlest piece of carbon that breaks off sounds like a detonated motor until it burns/breaks apart and is expelled. Ask anyone who owned an old Cadillac with those huge motors and they'll know what I'm talking about here. Sounds absolutely fugly.

[kcope]

I'll bet thats what it was. especially since the carbs need to be cleaned and rebuilt.

[scottb]

If you're worried, have your wrench do a compression test and leak down. That'll give you some idea of what's going on...and maybe some peace of mind.