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Any of you guys ever have this happen? I put new plugs in and I noticed the one at the back was loose. So yestreday I was doing a compression test and and that same plug was loose again. I know I tightened it when i replaced it.
Not an uncommon problem with some I6s. I had a 170 in a Ranchero and had to tighten the plugs about once per week. I haven't had that problem with any of my 300s.
I think it's just engine specific. I've probably seen the same amount of threads for complaints of spark plugs seizing right up (even if put in earlier that week) as I have for spark plugs that loosen up on their own.
Would a little loc-tite on spark plugs have any negative affects?
2 of my 300's do that. you can tell it's happening, it will flutter as you go down the road. sometimes the 1 truck will go a whole year without doing it, then will do it twice in 1 week.
neverseize is good. sometimes even then, they'll seize. the loosening plug thing is a pia, but you get used too it. noone said the 4.9 wasn't a hands on motor. hehehehehe.
mine did that a few times on almost every plug. i have found that from being loose the beveled edge gets kinda crusty on the head where the plug seats. I cleaned the beveled surface very well and have yet to have another problem with them coming loose.
I've had it happen as well. In fact when I put the fresh (60k miles on the engine and trans) drivetrain in the 86, I was going to pull the plugs on my old engine and I think 3 out of six could be turned by hand.