A good borescope can save tons of time and lots of money. The one I use cost ~$3000, and it's been worth every penny. It's an articulating type in which the business end can be inserted into a cylinder bore, or other small space, and then turn one hundred and eighty degrees and look directly back in the direction it came from. I've diagnosed scored cylinder walls, carbon build-up issues, bent valves, and blown head gaskets in a fraction of the time it would take to disassemble and inspect. I've also used it to inspect heater cores and evaporators. It's nice to be able to give a client an accurate estimate without gutting half the car! I've even used it to diagnose a few hard to find interior water leaks. We've had it for almost two years and I sometimes ask myself how we ever got by without it.