I just checked my spark plugs yesterday for the fun of it while doing some brake work and #3 was totally loose! I could take it out without any wrench at all, I put in the extension and turned and out it came!!

I know we have had threads here before preaching about checking the spark plugs for torque every now and then, I'm here to say do it!!

No damage to the engine or plug since it seems I caught it fairly soon after it became loose.

I'm running Iridium plugs and don't know if for some reason they come loose easier, but this is the first time I have checked them and one or more has been loose.

Just precautionary...it only takes about 5 minutes and is certainly worth it.

 

I'd add that over-torqueing them somewhat is a good idea, too. I installed iridium plugs to the specified 13 ft-lb before a track event; afterwards I checked them and one had loosened to no more than hand-tight. They're now installed at 18-20 ft-lbs.

 

[QUOTE]Originally posted by twohoos
[B]I'd add that over-torqueing them somewhat is a good idea, too.

 

Actually my mechanic strongly recommended I over torque them by a few lbs after we found they wouldn't stay tight at 13 lbs.

Use a bit of anti-seize compound and there shouldn't be any problems at 18 lbs. There's been some discussion that the 13 lbs torque is a misprint.

 

The plug manufacturers publish a range for each type of plug and head material. None of them are lower than 15-18 lb.ft. (some are 18-20) for our setup.

 

All you strong arms just remember that the head is aluminum, which will not handle the torque that steel will.

You do not want to deal with repairing stripped threads in the head. This is one area that I'd always go with Honda specs, and as mentioned use thread lubicant to be sure you are really getting what the torque wrench says.

Also remember that the washer on the spark plug is a crush washer. The torque spec reflects the amount of crush intended for good seal.

As to the misprint theory, I doubt that both the 18 N-M and 13 Ft-lb in the manual would both be misprints, and this is the same value.

FYI spec from other manuals I have on my shelf
Mazda Miata 132-192 inch-lb (11-16 ft-lb)
Ford V6 84-168 inch-lb (7-14 ft-lb)
GMC 350 V8 22 ft-lbs (but this is a steel head).
Massey Ferguson 1020 never mind, it's a diesel

 

Anti seize will make the torque reading accurate, but will do absolutely nothing to strenghen the thread against stripping from excess torque.

[QUOTE]Originally posted by Mikey
[B]

 

Some things to think about--

Aftermarket plugs seem to be causing problems for owners (loosening, even breaking!)

Torque should be checked when the head is cool, right?

Anti-sieze will reduce friction at the threads. The torque spec assumes use of anti-sieze. Without it, more torque is needed to tighten the threads to the same position.

Periodic inspection of the torque is better than overtorquing once

Just my contribution. Feel free to present your arguments!

 

[QUOTE]Originally posted by Gregg Lee
[B]FYI spec from other manuals I have on my shelf

 

Let me second the recommendation that you always use anti-seize. As previously mentioned, the plug threads are steel and the head aluminum. Thread these two dissimilar metals together, then add heat and time, and you could remove the threads from the cylinder head with the plug the next time you remove it. Thus the need for an anti-seize compound.

I won't enter the torque debate, but always use anti-seize.