Question About Spark Plug Torque Spec

[FlyingBiologist]

I'm getting ready to replace the plugs on my 2004 TJ with the 4.0L. I have a bit of a history with learning the hard way not to overtighten fasteners. So when it comes to potentially delicate (or expensive!) threads I try to use a torque wrench when possible. According to the Jeep service manual I have, the torque spec on the plugs for the 4.0L is 22 ft/lbs. However, while looking around online I keep seeing 27 ft/lbs cited as the correct value. Am I missing something or just being dense?

Thanks for any input!

 

[hear]

You’re probably over thinking it. 22 vs 27….it’s 5 ft-lbs. I would venture to guess that literally zero people here have ever actually put a torque wrench on a spark plug. “Pretty good hand tight with a ratchet” is fine.

 

[FlyingBiologist]

You’re probably over thinking it. 22 vs 27….it’s 5 ft-lbs. I would venture to guess that literally zero people here have ever actually put a torque wrench on a spark plug. “Pretty good hand tight with a ratchet” is fine.

That's a good point I hadn't considered: the small difference in the two. And honestly, I've never used a torque wrench on plugs before, just always gone with my gut. But I figured I'd try to "do it the right way" on the Jeep. I guess I'm mostly curious now as to where that other torque value is coming from for when it comes time to look up another one.

 

[SPECWAR]

Or if the have the tendency to over tighten stuff, cut you ratchet handle in half

 

[Head Lice]

Torque spec for dry threads or lightly lubed with 'never seize' or the equivalent ? It does make a difference.

 

[macleanflood]

The only vehicle I use a torque wrench for spark plugs is my V-10 Ford. It has 2-3 threads. Too tight and you strip the threads. Too loose and they fire out like bullets.

4.0 you can get away with anything.

Do keep in mind torque values charge depending on whether you use antisieze.

-Mac

 

[FlyingBiologist]

Or if the have the tendency to over tighten stuff, cut you ratchet handle in half

Hmm.... ya know, that's not a bad idea! lol!!

 

[FlyingBiologist]

The only vehicle I use a torque wrench for spark plugs is my V-10 Ford. It has 2-3 threads. Too tight and you strip the threads. Too loose and they fire out like bullets.

4.0 you can get away with anything.

Do keep in mind torque values charge depending on whether you use antisieze.

-Mac

That's another thing I discovered: I've always used just a small dab of anti-seize on plugs. But looking into the torque spec issue led me to Autolite's site (I'm planning on using the XP985) where they say not to use any sort of lubricant on the threads for exactly that reason: over-torquing.

 

[Danarch]

I’ve read the same thing on mfr’s website about anti-seize on plugs. I never used it and haven’t had a problem.

 

[JEEPCJTJ]

You’re probably over thinking it. 22 vs 27….it’s 5 ft-lbs. I would venture to guess that literally zero people here have ever actually put a torque wrench on a spark plug. “Pretty good hand tight with a ratchet” is fine.

5 is 20 some percent of either of those two numbers but you are right to say that “Pretty good hand tight with a ratchet” is fine.

 

[jonny jeep]

What I was told as a kid and still do to this day is screw the plug in till it bites, and give it a quarter turn. Never had one come loose or be to tight to remove.

 

[hear]

5 is 20 some percent of either of those two numbers but you are right to say that “Pretty good hand tight with a ratchet” is fine.

The % difference is helpful for dramatic effect, but it’s still only 5 ft-lbs. if the spec was 1 vs 2 ft-lbs would it matter more because of the 100% variance?

Your torque wrench in all likelihood isn’t calibrated to within 5 ft-lbs.