[Walt Fricke]

There must be some ways of adding suspenders to well greased cutting tools when preparing the hole for an insert.

One way guys change valve springs on an intact motor is to shove a bunch of string down the plug hole, and then bring the top of that piston up until it presses the string stuff against the valve heads. Of course, you leave an end of the string out so you can get it back out.

If you have a hemostat, or a grabber, you could probably reliably get the in through the plug hole to retrieve it. My notion is that you could grease the string liberally, and extracting it might get any chips which got in back out.

Nobody is going purposely to put aluminum chips into a combustion chamber. But a few small ones seem unlikely to cause any serious harm. I once decided to attach carburetor air horns through the air filter base with slot head screws rather than the studs and nuts which were usual for the purpose. The screws backed on the track eventually, the horns moved, and some small steel screws got sucked into various combustion chambers. I could hear when it happened as my wife was taking the final few laps of a race.

Some of the screws were spit out the exhaust. Some were embedded in the head or a piston. All this cleaned up reasonably well (no valve damage)though hardly perfect internal cosmetics.

While drilling/threading you might be able to blow air in the intake so it would come out the plug hole while you worked. Having a bore scope for use when done would be useful - you could use it to see what might have gotten into the combustion chamber. The grease on such chips might allow you to use the scope to fetch them out.

And someone who has done this on an intact engine may read of your problem and have better practical advice.

I'm assuming pulling the engine so you don't have to work while a pretzel is in order here. If you can put the engine up on a stand, you can rotate it so the plug hole faces straight down. A bit more awkward working on it, but you'd have gravity on your side relative to chips.

We are often cautioned not to put anti-seize on the plug threads, sometimes by guys with darn good credentials. But I'm more afraid of damaging the threads in the heads than I am of the plug not having good electrical connectivity to the engine, so I have always used anti-seize on the plugs for my VW and Porsche air cooled, aluminum head, motors.