Is there some kinda telescopic tool and camera combination you can insert through the spark plug hole wherby you can see the condition of cylinder walls and face of the valves etc? Kinda like what the scutineers use at WRC rallying. What exactly is it called? Is it expensive?

 

they're called borescopes we use them at work from time to time to look at the power turbine blades and sometimes compressor section (depending on stages) of the helicopters powerplant. they are (used to be?) very expensive - especially the ones that can bend in two directions not just one direction... we rent the item rather than have one around 24/7 because of the expense.

 

if you have any friends in medicine- they have plenty of cameras designed to go in small places!