#8 Spark Plug Wont Thread In All The Way

[Reynolds Rides]

Hey Guys,

I just bought a 94 ZR1 with 123,000 miles. I recently noticed that the #8 cylinder plug wire sits higher than the others. I have been able to determine that the #8 spark plug is not threading in all the way. I have removed and re-installed the plug about 3 times now with no apparent issues except for it not going in all the way (about 4 threads wont go in). There are no signs of cross threading or obstructions down the hole. I pulled the #4 cylinder plug to compare it to the #8 plug and they appear to be the same (all of the plugs currently in the car are Autolites) but when I tried to install the #8 plug into the #4 hole, it only went in a few threads. Also, the seller gave me the old set of spark plugs (AC Delcos) that he had removed and I tried to install one of those into the #4 hole and it would only go in a few threads as well. But, the #4 plug threads into the #4 hole all the way and without any issues. Hopefully that makes sense. Weird, right? The car seems to be running well but I would like to fix this. Any help or advice would be appreciated. -Jeff