I just got back from AutoZone with my new plugs. Pulled the first plug with no problem. I'm putting the new one in (With anti-sieze) and it just gets tighter and tighter as I turn. about 1/3 of the way in and I'm putting a lot of effort into tightening this plug down. It feels way harder than I think it should be on an aluminum engine. I backed it out and compared the old and new ones. They're the same thread and everything. I'm trying to put NGK BPR6EY-11 plugs into an EA82. Any advice?

get a spark plug chaser, not worth ruining your threads in the heads. grease the threads of the chaser to make sure any shavings stick to the chaser.

Wait until the engine is cold.

 

You pulled the plug while it was hot, then the exposed threaded hole cooled off quickly, shinking.

 

Never ever pull sparkplugs from a hot aluminum engine.