Drop $400 on a bore scope I thought was a gimmick. Best tool I own now.
Honestly, everyone told me to just stick with a basic inspection mirror and feel for cracks. I dropped $400 on a high-res bore scope from Snap-On after my third failed head gasket guess. It paid for itself in two months by spotting a hairline cylinder liner crack I never would have seen. Now I use it on every major rebuild and it saves me from rework. Anyone else swear by a tool they thought was overpriced at first?