If your good with tools they actually sell drill bits that make threads but you would have to buy a new spark plug of a different size, which might be a pain in the ass. You can try the locktite method... Just but some lock tite and try to thread it as best you can and it shoudl stay in. But I would buy a really good set of plugs for the car... like platnuims or something so they last for 20,000+ miles, because once its in there your really not going to have a good time trying to get it out.