Spark plug thread repair - GIF

[nova_robotics]

If a guy is real careful with a powerful vacuum over the hole while drilling and tapping. possibly using a special adapter to fit over the hole that he can pass a drill bit or tap through he might get away without losing any chips down in the cylinder bore.

Could probably roll the crank over until the intake valve is open then blast compressed air in the intake valve to blow chips out while tapping. That might be the best bet. I still wouldn't trust it 100% though.