I was thinking it would be nice if I could look at the valves without having to take too much stuff apart. Could I thread a small endoscope down through the air intake and be able to see the top / backside of a valve? Could I put one ( bent backwards ) down the spark plug hole to see the cylinder side of the valve? It would be cool if I could do a before and after of how cruddy the valves are when I psuedo-seafoam the intake.
The tool you seek is commonly known as a borescope, which should allow you to inspect both sides of the valves if you can get the scope end to reach there.
Here is a nice YouTube video showing the inspection of the piston surface and cylinder-facing side of the valve: https://youtu.be/LgbhePnUHiI