Borescope vs. old-school mirror check, which one do you trust for cylinder scoring?

I was doing a compression check on a Continental IO-520 at Paine Field last Thursday and found a score that the mirror and flashlight missed completely. The $3,200 borescope showed it plain as day, but my partner swears a good mechanic can feel it through the spark plug hole with a wire. I get that the scope is pricey and needs WiFi to save videos, but the mirror left too much guesswork on a $14,000 overhaul call. Has anyone else had a high-stakes call go one way or the other with either method?

2 comments

2 Comments

zarat3710d ago

Did your partner actually find scores with the wire, or just guess?

the_rowan10d ago

Honestly, I think a lot of the "science" in picking is just solid habits and avoiding the obvious traps. It's less about magic wires and more about not panicking when the spreadsheet says something you don't like.