My roller moto 302 in my z28 did a freaky thing...

[Rixls6]

I had a similar thing happen to an engine with a 2-piece intake once.

One of the bolts inside the intake that hold it to the head came loose. When we fired the engine after sitting for a while, the bolt lodged in the intake valve and caused a similar explosion.

Both valve cover gaskets blew out, the oil pan mushroomed out and blew it's gaskets, and both mufflers blew out.