Buddy of mine found this when changing the oil. It resembles a valve lock but has splines. He said he changed the oil 200 miles ago (piece wasn't there), changed it yesterday and found the piece.

Prior to the discovery, he said the car drove fine and didn't make any unusual noise.

I've only seen the attached pictures and haven't seen it in person.

Nothing has been done since it was found. I.e. no teardown, etc...

Engine is an LS1 based 383.

 

Looks like a piece of a bronze, press-in valve guide

 

Are the top and bottom surfaces machined smooth or does if have a broken edge?

I was thinking valve guide also but then one surface has to have a broken finish. If both are machined then it is not a guide. It is probably a bushing for something if both are machined.

Also, how does the valve guide piece get out of the seal, through the spring, and into the oil pan without being noticed somehow?

If the guide breaks and falls into a port then it either goes out the exhaust or through the piston.

 

Rocker arm point where the pushrod pivots or pushes on?

 

I haven't seen it in person. He is going to start investigating Friday. I told him to call me if he wanted the help.

You are the second person to mention it may have something to do with the rocker arms. He is running Yella Terra arms.

 

Update:
It was a pushrod cup from a rocker arm.