To keep metal chips out of the engine while tapping you should cover the tap with grease. (Just your normal chassis lubrication grease you find in a can at any autoparts store).
Cover the drill bit or tap with grease
Drill or tap a little bit
Wipe off the grease and chips
Repeat until finished.
Don't try to save grease, whip it off and replace as soon as you see some chips sticking to it. Likewise cover the area around the hold with grease so the chips stick. You will use a lot of grease and paper towels but if you go slow and steady you won't end up with chips in the engine. I've used this method a couple time to fix spark plug holes with the head still on the engine.
Also I recommend threaded sleeves over helicoils.
https://www.mcmaster.com/thread-repair-inserts