Cheap eBay endoscopes

Yes.

The endoscope worked just fine. The laptop wasn't very good in outdoors with sun.

It wasn't a good experience. :-(

Thanks for sharing the image. That's pretty much what I'm thinking of. I'm trying to find out if the rattling noise from my engine is caused by pinking, or just a rattle somewhere. If I could see the crowns, it might help me decide.

Are you certain a cheap endoscope is small enough to fit through the plug hole?

it is quite easy to find an 8mm one, the difficulty is in pointing it in the right direction and getting it focussed, and then interpreting the picture.

Yes as that's what was used to take that photo.

It is the type with an outer sheath made from a plastic covered wire spiral and can be bent to a shape that it will retain. It has also managed with a bit of pre-forming to get past the throttle plate and down No1 inlet.

The sort that are just a camera on a bit of flex would be useless.

All true. And seeing the monitor outdoors, as has been said.