The past week I've been doing a lot of 'homework' in studying up for my intake manifold remove & replace. While I have it off, I'm going to replace the spark plugs. Now that my codes are gone- a plastic guide on the engine cover has sharp points that rubbed through my PCV hose- I missed on first inspection. It wasn't until I cleaned the MAF & changed the air cleaner filter that I noticed the hole. It was a problem just waiting to happen- a Dremel will solve that from happening again.

Anyhow in my search I came across many threads that advise against the use of anti-sieze on spark plugs and show pics of the results- broken plugs! The thought is that the antisieze is causing people to over-torque the spark plugs. I've read the same thing about lug nuts. I use a torque wrench to torque my lug nuts except one time and had one heck of a time removing the lug nuts then next time.

I just read the thread on changing the knock sensor and plugs which is great. I am simply wondering about the use of anti-sieze on the plugs and what the experts thoughts are. Thanks

 

You will find a lot of talk about the use of anti-seize. I use it all the time in both my Jags and use a torque wrench to prevent any stripping problems. I feel the lack of proper torque is part of the problem.

 

Backhertz, you are getting into what I spent years learning inside the navy and how torque is not simply torque when you start changing characteristics (ie application of a lube when supposed to be dry, different lube used, methods of torquing items).

The short of the story is that when you have a joint that is not assembled using lube, the running torque of the item is much higher, therefore, some of the torque that you see on a torque wrench is simply what is needed to make it turn. This value becomes greater as things start to tighten down (in a dry application, more on this later). When it comes to plugs and lugnuts, it is assumed (gotta love that word) that they are being applied dry, therefore the applicable torque is calculated using this thought process. If you like to be proactive and prevent things from binding up on you in the future and you apply a lube, you are now reducing the running torque, so, more of your twisting action is going to go into the clamping force (what you are truely after). But, keep in mind that for a given bolt manufactured a certain way, it can only handle so much force. So, if you applied something like say Molykote P55 lubricant, this changes the necessary torque to get the desired clamping force by about a factor of 0.8. So, without lube, if the item needed 100 ft-lbs of torque, to get the same clamping force with lube, you would only need to use 80 ft-lbs of torque.

Not to get technical on you, but keep in mind that when you have a clamping force, the fasteners are "stretching". Yes, the fastener is getting longer. We are normally talking on the scale of .001" or so. But, you are still pulling the metal apart. Hence why things like head bolts can only be used 1 time because as you stretch a bolt, it becomes stronger (to a point). Some engineer figured out at what point the bolt will reach its yield point (ie, its strongest point). that is what head bolts are torque to. So, the next time you go to use them, if you tightened them the same way, you would actually go beyond yield strength and have a very weak bolt holding the head in place. I think you can see where this might get ugly.

In the case of spark plugs, if you have a head with only a few threads holding the plug in place, if you apply an anti-sieze/lubricant to the plug, you can easily exceed the yield strength of the head material (technically, most plug threads do not have the necessary material left to make a proper joint, so the head material is the weak link). So, if you torque the plugs to what the manufacturer recommends and use an anti-sieze compound, you may very well damage the head and not know it. So, a little while later as the plug takes pounding after pounding from the cylinder firing, it will finally fail and launch the plug (this is called cyclic failure).

If you want to know more, let me know. I can go much deeper into this subject. Gotta love knowing how to torque bolts to millions of ft-lbs using nothing more than a heating rod. I am also certified to torque by feel. yes, I can grab a wrench, apply it to a bolt and say that is it torqued to XX ft-lbs. Not quite that easy, but that is the general idea.

 

One way to avoid all the hoo-hah is to torque dry a few times and observe the angle required. Then, lube the threads and torque to the same angle. It will be the same clamping force. Once the angle is known, a torque wrench is no longer required. Quite handy if one happens to breakdown without a torque wrench handy.

Almost all spark plug manufacturers also publish guidance for torque to angle in addition to both dry and wet torque values for each of their thread types.

 

This is not giving you or any one a hard time just want to put in perspective. So would you torque a % under the stated value it makes the process consistent and safe so not to launch a plug? I think the bigger problem is under and over torque. Not to apply the anti-seize is a problem as well. What is the solution?

 

Gus there are down sides to both, there are plus sides to both. Personally, I put my plugs in dry since they were designed to be done that way and if I have a problem getting them out, I use a bit of PB Blaster or the like and they seem to come out without any problems. I am sure there are other people that swear by the use of anti-seize compound.

Granted, I am also the guy that uses more of a angular torque than putting a torque wrench to the plugs. Been good so far. Never had a plug blow out on me other than in my truck which has a design flaw from the factory and even then I lasted a lot longer than most did.

As for a new value to torque the plugs to, I would say to torque the plug to 80% of what the dry torque is. Most lubricants have a reduction value of about 20%. So, if the plugs are required to be torqued to say 15 ft-lbs, then you would take 80% of this and torque the plugs to 12 ft-lbs. But, start with what is recommended by the manufacturer as they have already factored in the head material, number of threads, etc. Unless you have a special book that allows you to find the necessary torque, you can do more bad than good.

 

Agreeing with all the comments so far.

I use lube on EVERY nut and bolt ALL the time.

This has come basically from V12 ownership, where spark plugs snapping off is common. Not getting technical about that disaster at the time, the thing broke, I need to fix it. The HE with the taper seat plugs are worse than the PreHE, which uses flat seat style with a single use crush washer.

I also use a torque wrench, mostly, and 10% less than specified due to the lube, and the EXCELLENT explanation above. Wish my teacher in the '60's was that explicit.

As also mentioned, this discussion could end up like "which oil is best for my car", so at the end of the day it is your car, and if it is even slightly going to be a "keeper" do the best that is out there at this given time.

Our V12's are loooooong time in the fleet (20+ years), and once "up to Grant's spec", as in lubed everything by me, maintaining is simple and easy.

 

The solution for spark plugs is torque to angle. The clamping force for a given angle, whether dry or wet is the same.

The information is available on reduction in torque wrench value for various types of lubricants. But the people who come out with the internet edicts and those who discuss them do not seem to be willing to put the research hours into the task.

Like Thermo, I often torque by feel. I will even override the specified value if I deem it wise given what I am feeling through the wrench on that particular fastener.

 

I'm interested in rumours about anti-seize supposedly having other negative side effects. Anybody?

 

On spark plugs, or anywhere?

Never heard about problems on spark plugs unless it's glopped on with a mop and fouls the business end :-)

Cheers
DD

 

Since the overwhelming majority of torque specs are expressed as an acceptable range rather than a single exact number it might be easy to simply stay at the low end of the specified range.

Just a thought. No mathematics involved !

<shrug> <grin>


Truth is, I use a torque wrench only for a small handful of specific tasks anyhow. For most fasteners I use my built-in angle meter. On the occassions when it gets sore I have some 10 year old amber colored "rheumatism medicine" in the kitchen cabinet :-).

Cheers
DD

 

I use antiseize but reduce the torque by about 25%. Has anybody studied the amount any rust reduces the clamp load? Herre in rust belt Michigan, that is a greater problem.

 

On spark plugs specifically.

 

MIkey, in the case of plugs, anti-seize compound could lead to issues because it can get baked into the threads and actually act more like a thread locker than a lubricant. I have seen what anti-seize does inside of salt water systems. Not good. This is where knowing the characteristics of the anti-seize that you are applying as to whether it will be beneficial or hurtful. This is kinda like saying that you car is blue. Are we talking light blue, dark blue, with metal flake, etc. To make a generic statement does not adequately cover the topic. Specific lubricants are made for specific applications. I liken it to thinking about putting gear lube in your engine. It will work, but is it the best for the engine?

 

As Doug said, "unless glopped on.....".

I use a smear on spark plugs, and always have.

I also have NOT gone down the scientific/theoretical path. See no need.

Items require changing from time to time, and if the old comes out trouble free thanks to some addition substance, GREAT.

Snap a plug off, anti-seize suddenly becomes your best friend.

Those of us old enough to have needed to remove the front lower wishbone pivot pin on the earlier cars where the factory installed them "dry" swear be anti-seize, and swear a lot in general anyhow.

 

FWIW for spark plugs I've always used the silver stuff from Permatex

Cheers
DD

 

We are talking torque and angle torque but should that all be calculated knowing the shearing point of the product in this case the spark plug and head qualities?

For what it is worth I replaced the plugs in my xk8 when we first got it. After many miles I elected to change them again but when I did I found several were loose (hand tight), I guess I did not tighten them properly “no torque wrench” but did not want to strip or shear the plug. Today I think it is wise to use a torque wrench for many reasons and the one most important is to prevent over tightening. As you know over tightening on an aluminum block could be devastating and the lack of anti-sieze could be as well. I use a torque wrench and anti-sieze often. I will apply less torque the next time and see how it goes.

 

Holy cow. I didn't mean this to be a controversial question or like a what oil should I use type of forum question. I have seen that latter question so many times on other forums by newbies who probably should not be doing anything to their engines.

One time I was using a friend's swimming pool while he was away. One of his son's friend's was working on his car doing an oil change in my friend's gaage/driveway as he was house sitting. As we drove up, I asked him if he was okay. He said yes. I left him alone & took my daughters, their friends & dog to the pool. An hour later or so I wandered out front & the guy is still trying to get the drain plug out!

I asked him if he was okay & he said no. He has stripped the head off the plug and was down to using vise grips. I watched him for about a minute & asked him if he considered turning the plug CCW??? This is the honest truth. He said no & tried it & voila the plug came out. I went back to the kids.

A week later, my friend was back home & the kid came in. He said his car broke down on the Interstate. I asked what happened? He said he was driving down the road and the engine started making so much noise, he had to roll the window up & turn the music up. Those were his words! The engine seized…

I have always put spark plugs in by feel and never experienced any issue. Anti-seize to me is like white thermal paste used on high power transistors- you use it & it seems to get everywhere. But never the less, I have used a tiny bit of anti-seize on lug nuts in the past, but I only use a torque wrench and torque to manufacturer's specs. I never used an impact wrench to tighten/torque lug nits. I've had problems in the past when I lived in NY State where we had mountains of salt used in the Winter to keep the roads free of ice. But oh boy, cars did not last long & it didn't take long for salt to accelerate the corrosion process.

In my work on large radar systems which used huge coaxial connectors, I would cut the wrenches in half at radar sites to limit the amount of torque technicians were able to apply as some would strip the connectors. A 6-inch wrench seemed to eliminate that problem. I'm not sure why and when I tried to explain the process, I would sometimes be talking to people like the kid who never considered turning the plug CCW. I simply told them I was giving them a special torque-limiting wrench & they were happy & stripped coax connector issues almost disappeared. There were some who "knew" better and would go out & buy 12-inch wrenches and you know the rest of the story.

I understand Thermo's explanation and I know everyone has their own experience. I've only seen one plug issue on a Mercedes where a guy over-torqued the plug and stripped the threads on the aluminum head. I had to remove the bottom of a broken spark plug in my mother's Ford. It was no fun, but it was at least accessible.

Thanks everybody. Since 1970, I've changed a lot of plugs & never thought I'd see plugs that lasted 100K miles. That's good, but I know that people's skills decline over time & it's been a while since I changed any spark plugs. I have some time & will wait for the Spring. I will most likely not use any anti-seize & simply torque to whatever the spec is.

BTW, I have no idea what happened to the kid who did his own oil change. That was 20 years ago. I honestly do not believe he ever attempted another oil change.

 

Lug nut studs are made with grafite additive

 

And now you know why.