Spark plug torque when using anti-seize

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SZR48207

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WHEN anti-size is used on spark plug threads prior to installation, what percentage of torque have you folks backed off from the dry spec?

I did the 30k plug change on my Tacoma and it feels like I set the torque a bit low, but the math works out based on the info I can find.

Toyota factory dry spec = 15 lb-ft

Denso's own spec for this specific plug (K20HR-U11) is 15-22 lb-ft in an aluminum head.

Denso also says to reduce torque by 30% when using anti-seize.

So I did 15 lb-ft minus 30% = 10.5 lb-ft torque on each plug.

It drove fine and didn't feel like I lost any power. All good I guess?
 
Some of the new plugs/manufacturers tell you not to use anti seize. But if that's what their website says you're probably ok. I always turned in by hand and then gave a ratchet a moderate turn until it stopped, whatever that might mean for ft-lbs...
 
You need to find the K factor of the product used. AS can have a significant K factor. Light machine oil is around 0.15 as I recall. AS can be as high as 0.4-5.
 
Originally Posted by Ws6
You need to find the K factor of the product used. AS can have a significant K factor. Light machine oil is around 0.15 as I recall. AS can be as high as 0.4-5.


Most websites I just Googled say to reduce by 15-20% if you can believe The Google. The NGK Laser Iridium whatever name they had I used didn't need anti seize. Some factory coating on the threads.
 
I use a little bit of Tri-flow oil and turn them in until they're tight.
There's lots of engines out there where a torque wrench will never fit.
 
Originally Posted by Reddy45

Toyota factory dry spec = 15 lb-ft

Denso's own spec for this specific plug (K20HR-U11) is 15-22 lb-ft in an aluminum head.

Denso also says to reduce torque by 30% when using anti-seize.


Looking at Denso's numbers, I'd almost believe they already told you what to use when using antiseize: 22 lb-ft x .70 (30% less) = 15.4 lb-ft.

Your number of 10.5 seems AWFULLY low; maybe Trav can weigh in, but I'd think you're risking blowing a plug out at that low. If I were you I'd personally torque them to 15 with antiseize.
 
I just looked at a tube of "Permatex Anti-Seize Lubricant" I have, and on the back it says: "Apply a light coat to part. Assemble and torque to manufacturer's soecifications".

So apparently the stuff I have must not change the torque spec enough to worry about.
 
Originally Posted by ZeeOSix
I just looked at a tube of "Permatex Anti-Seize Lubricant" I have, and on the back it says: "Apply a light coat to part. Assemble and torque to manufacturer's soecifications".

So apparently the stuff I have must not change the torque spec enough to worry about.

I find that impossible to believe.
That said, I also find it impossible to believe that anything sensible matters. It's when you go all stoopid that threads get stripped. I have never used a wrench to do plugs, even on aluminum blocks. I just use common sense and realize that I am not trying to plug the Hoover Dam with the thing.
 
Originally Posted by SubieRubyRoo
Originally Posted by Reddy45

Toyota factory dry spec = 15 lb-ft

Denso's own spec for this specific plug (K20HR-U11) is 15-22 lb-ft in an aluminum head.

Denso also says to reduce torque by 30% when using anti-seize.

Looking at Denso's numbers, I'd almost believe they already told you what to use when using antiseize: 22 lb-ft x .70 (30% less) = 15.4 lb-ft.

Your number of 10.5 seems AWFULLY low.

10.5 ft lbs is 126 inch lbs if that number feels better. I currently have 20 spark plugs torqued to that using Permatex 133H anti-seize. No problems.
laugh.gif
 
Always go by the engine manufacturers torque spec not the plug makers, plugs are usually not specific to one particular make (there are exceptions but this isn't one of them), thread count may vary hence the 15-22 ft lb recommendation.
10.5 ft lb is almost 15 Nm which is enough in an aluminum head with never seize.
 
Other than Ford 2 piece plugs... can you really overtighten one? Ok, if you use a breaker bar to install, sure. But other than that... Just what bad is going to happen if you put in at 50 ft-lb instead of 10? Or if you put in at 2 instead of 10?

I'm not sure how this is any more sensitive than an oil filter.
 
My Honda Accord V6 FSM specifies anti seize on the treads and tighten to 13ft/lbs (14mm gasketed plugs). When I took out the original NGK plugs, anti seize appeared to have been used at the factory. My Permatex can also says to apply to fastener and torque to the specified torque. I did a little research on this topic and it appears anti seize on threads has little effect but applying under the bolt head does. As the saying goes, YMMV and use caution. Lots of contradictory advice out there, it is the internet after all.

This topic never dies.
 
I never have used a torque wrench on plugs. The last 2 sets I change it said right on the box, to just lightly seat and give it a 1/4 turn. In that case it doesn't matter if you have lube on the plugs. You can even feel when it is tight enough, and on some things you just don't get the feedback from a torque wrench like you do from a regular wrench.
 
Sure you can over tighten them just like any other threaded fastener. On some engines like the old Ford 2v modular it doesn't take much either before you rip the threads out.
Steel plug threads vs aluminum threads in the head, aluminum looses every time.
 
Adding anything to the threads WILL change the K value (Wrench Torque = K *Axial Force*bolt dia )

Most anti size manufactures will list K values for their anti-seize. You may email permatex for an answer but I found these with a quick google.

Quote
In the case of Permatex products the K factors are -

* Standard Anti-Seize K = 0.18
* Copper Anti-Seize K = 0.16
* Nickel Anti-Seize K = 0.13


If Normal Dry threads are 0.2, and std AS is .18,

So for example using 15 ft/lb or 180 inch-lb with M14 thread

180 in-lb = .2 * F * .551(M14)

Solving for F (Axial force or clamp force)

Dry Threads Axial Force (Clamp Load) = 1633.4 lbs
Standard Anti-Seize = Axial Force (Clamp Load) = 1814.9
Nickel Anti-Seize K= Axial Force (Clamp Load) = 2512.9

11% Increase in clamp load(std AS), for the same equivalent dry torque you can lower your wrench to 162 in-lb or 13.5 ft/lb when using Anti-seize.
Nickle though that's a whopping 54% increase in clamp load, you would want to lower your torque values accordingly. To 117 in-lb or 10ft/lb

In reality, YMMV as K value is different with every bolt, anti-seize or lubricant does even that variation out but, when you add the friction of the head into the calculation, your preload/clamp force can actually vary more than 11% with a torque wrench(±25-30%) so that is likely why permatex says to use normal torque spec, as it is within error.
 
I spray a little WD-40 down the plug hole to clean the threads, especially on older engines. Cleans out old anti-seize, etc.
Then just a tiny amount of anti-seize towards the bottom of the plug threads.
Reduce the torque by perhaps 20%.

I run the plugs down by hand with a rubber installer, mainly to feel for any restriction.
Of course I like any excuse to use my inherited flex head Snap-On torque wrench.

I know many feel this is wrong, but it is how I do it. Later removal is a snap.
It drives me crazy when plug removal requires tons of torque.
 
Jeff never EVER use WD40 near an engine!

The silicone in the WD is a Lambda sensor killer.

On Gasketed plugs. Just like a drain plug with a new washer.

Tighten until the gasket crushes and you feel the torque start to ramp ramp up - then stop.

Non- gasketed use the stretch angle specified.
 
Per the manufacturer WD-40 does not contain silicone. Besides, it's going in the combustion chamber and not directly into the exhaust stream.
 
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