A bit misleading as this is in regards to air-cooled aircraft engines but I was curious on anyone's thoughts on these procedures. Airplane folks are usually pretty particular about their maintenance but it appears they will take shortcuts when they have some data to back it up. Would you do this to your engine to avoid a teardown? Solvent Ring Flush
Been doing it for years especially on direct injection engines that clog the intake valves and ports up with junk.
Putting abrasives directly into the cylinder would freak me out. Looks like works though. Pretty slick.
I have seen bent valves straightened using a similar technique. Remove the spring, bring the piston to TDC, rotate the valve so that the low spot comes in contact with the piston, and then hit the tip of the valve with a brass mallet as necessary to bend the valve. Once the valve has bent back as straight as possible lap it in using the method outlined in this video. The repair might not be sufficient for a race motor, but it is likely to suffice for a cheap fix on a daily driver when you can't afford to be without transportation for a week in the repair shop.
...that bothers me more than in place lapping. Even for a DD, I'd worry I've added more metal stress and increased chances of valve head separation...
