[ItBites]

I'm with Keith here mostly. The white pieces look like teflon and in the first picture you can see what looks like rust or metal staining the inside, which looks like they were around probably iron guides, but maybe bronze guides. The metal pieces look like the interlocking 'fingers' from the type of teflon valve seal that has the flat band around it. I know some of the pictures look like this is wire, but thats because the photgrapher stood them up on edge - you can see in the first and the third photos the shiny metal is flat and curved.

The black stuff is certainly gasket materal and it also looks like you found a piece of red silicone as well, but you could tell for sure if it is rubbery.

The gasket material and silicone could be from this build, but you really shlouldn't get that. If this si the result of a sloppy re-build and they left some old gasket and silicone lurking about, the teflon and tension band pieces could have been left from a previous build as well.

You really need to look inside each valve spring for the valve seal. They will be white with a wire or band tensioner around them. The wire or band is usually silvery, like the debris you found. If they are all there and not damaged, this may be from a previous failure and not removed during the following rebuild.

If you find damage, you need to repair it AND look for retainer interference or some cause like Keith said (the seals should not fail on their own). If you find no damage, you're probably OK to just seal her up and go on... probably... but know your engine may have more chunks in it...