glmoore0001

Plug torque from what I have read around here is about 20 foot lb.

Is this correct? From the feel of it, it doesn't seem like enough.

Thanks Gary

jennifer911

Gimoore, in his shop, my dad always told people that a torque wrench is a very indirect way of reading how tight a bolt may be. The feel you speak of generally relates to the threads binding against each other. If the threads are dirty or deformed, what may feel good and tight may not be. On the other hand, if you have followed the general best practice for aluminum heads by coating the plug threads with a bit of anti-seize lubrication, the threads easily overcome a lot of extra friction. 20 ft-lb torque with an extreme friction lube may tighten down a plug more than 30-35 ft-lb with dry threads. Your sense of feel can be fooled by this.

Typically wheel lug nuts use a dry torque wrench setting. My dad would curse people who would use anti-size on the wheel lugs of vintage and antique cars then set the torque wrench good 25% higher. These old fatigued parts would break when he worked on them.

Just an aside, many mechanics and experienced people eschew the use of torque wrenches on common parts. They trust their practiced arm to know the exacting amount of tightness. Widespread studies have shown most of these “I don’t need no stinking torque wrench” people over-torque small nuts/bolts and under-torque large nuts/bolts.

Rob Edwards

Factory torque spec is 18-22 ft-lbs. May not feel like enough but it is. I trust my torque wrench way more than I trust myself.

glmoore0001

Thank you for replying Jennifer.

Yes, I am one of those old school mechanics who thinks that sometimes torque figures are put there because some engineer had to have something in the specs for the Factory Workshop Manual.
When I am working on Detroit Iron it is " Make everything RFT (real effin' tight)" because I can go to a yard and pick something up if I screw it up or just Helicoil it. Not so much here.

I was also taught that, with torque figures in mind, that it had to do with a clean dry bolt, no lube, no anti seize, so that is the way I build.

Everyone has differing opinions, you only know you are wrong when your fastener backs off or (god forbid) you pull a spark plug thread.

With that in mind, I will go back and retorque the plugs that I am wary of (the first two that I installed) while I wait on weird air filter adapter housing o ring that was so hard you could cut diamonds with it!

Have a nice day J... Gary Moore

glmoore0001

Thanks Rob. Just checking to make sure there has been no forum revisions to the figure.

.. Gary Moore

jcorenman

Unless specified otherwise. It is correct that torque specs will be different for dry vs. lubed threads, but the 18-22 ft-lb torque spec is for lubed threads. See WSM pg. 28-9, "Replacing spark plugs":

glmoore0001

So there is supposed to be lube on the threads per the book? Ok. That is a good piece of information to have. I will start over.

I had read discussions on here whether to use anti seize or not. I was unaware that the book speced a lubed plug.

Thanks everyone for the replies.. Gary

Mrmerlin

Gary by starting over you mean that you will remove the plugs again?
I would not touch them,
there should be enough anti seize in the plug threads for this installation.

When you replace the plugs the next time then use antiseize

glmoore0001

Thank You Stan! That is good news!

Mrmerlin

if you look on the plug box you may also find a diagram that shows the plug once lightly seated to then turn it about a half revolution this will also work as you will feel the crush ring crushing

jennifer911

glmoore, if you were able to easily spin the old plugs out by hand after breaking them loose with a wrench, then as Mrmerlin mentioned they probably had some residual lubrication. However, if they made squeaking or creaking noises as you backed them out with your ratchet, then the threads are dry and galled and need lube. Also the lube is necessary for the torque value to be correct. Although I doubt my dad used his torque wrenches on most spark plugs. He could expertly feel the exact point that the plug seated and how much more pressure needed to set in place. There is an aero museum in Kansas somewhere that has an early 1900s specially cast all aluminum airplane engine that my dad reconstructed from a pile of dust. He plated the threads of the ancient spark plug shells in silver to provide a friction free noncorrosive seal. So he did have a fine touch for these things.

One of the dangers of dry plug threads is the long service life (of modern spark plugs) with all the heat cycles can cause a plug to fuse in an aluminum head. Anti-size or premium priced plugs with nickel alloy plated threads helps prevent this.

Bill Ball

Lubing no longer applies. The plating on plugs eliminated this. Porsche changed the recommendation retroactively in this bulletin.