I’m fairly new to my 80 series. I’ve done a ton of work on it and have run into a few issues that I can’t figure out. It’s a 1994. Shortly after picking it up I developed a top end knocking noise. Upon investigation I found that a couple spark plugs, that were in Reasonably good condition upon inspection, had stripped their holes. I installed Perma coils in the affected holes and obviously changed the rest of the plugs. Long story short, the cylinder 3 plug is having issues. The plug and Perma Plug threads that go on plug that protrude into the combustion chamber are experiencing extreme heat and burning up. At least that is what it appears to be. Wish I had pics to show the plug but believe me that there is not much that’s left that’s metal on the plug in cylinder 3. It’s happened at least 3 times now. It runs beautifully until it gets burnt up. No noise, no issues until it doesn’t provide spark anymore. Any thoughts on going forward. I plan a rebuild but am trying to figure out why this is happening and how to avoid it in the future. Thanks!