question about damaged sparkplug thread

[frosty]

hi guys

This isn't about a M-B but it's more about cars in general. I was wondering what happens to the aluminum pieces that fall into the sparkplug hole when a thread gets damaged? This happened on my Volvo (240) to one of the plugs. I have heard that the Al gets shot out of the exhaust and there is no need to worry, and I also heard that the Al and any gunk may fall into the engine and get mixed with the oil and there is need to worry. I did a search and it seems that it is evenly split between "no need to worry" and "WORRY!"

I took my Volvo to a shop where the mech. said the thread was not majorly damaged and he was able to salvage it by "tapping" it. He said it did not need a heli-coil. Is it possible to fix a sparkplug thread without using any replacement parts? Exactly what did he do by "tapping" the thread? The car runs fine and does not sputter, but I am concerned about driving it on the freeway or working the engine hard for fear of shooting the sparkplug (the one in the repaired thread hole) out of the engine head. I heard that can happen. He said it's as good as new and that I should not worry. What about the Al pieces that fell into the sparkplug hole? What are some of your experiences concerning damaged plug threads? Thanks guys!