Optimax Stripped Sparkplug
So I am working on a 200 Optimax (3.0). Plugs looked like they hadn't been changed in a while and cylinder #2 was tough to get out. Looks like someone at some point cross threaded the first couple threads and you can see that they're pretty gummed up. I could force the sparkplug in but I would rather not do any more damage. Luckily the majority of the threads look perfect after you get past those first couple of turns
I have tapped holes before, never something quite this large. In my research I have found what is called a back-tap which threads from bottom to top, or from inside out. This seems perfect for this application because I want the tap to start at the threads that are perfect and continue up to wear they are damanged. I feel like if I were to tap the normal way I may not fall into the originall groove and may end up tapping new threads altogether. Any opinions on the matter? Seems pretty straightforward but maybe I am missing something.
Thank You