Changing spark plugs - do I need Anti Seize?

Originally Posted By: onion
Can you give any more detail about your research into fastener clamp loads?

I'm of a similar school of thought- I know what you're getting at when you talk about how much clamp load can be affected by corrosion, worn parts, lube or lack thereof, etc. In many cases (though definitely not all), I trust my own feel more than I trust a torque wrench- but I wouldn't recommend that for everybody (I've been tightening all manner of bolts on a daily basis for 15 years, so I'm pretty confident that I can get them 'close enough').

Lots of people on this site are very "by the book" in their mentality. And that's fine- 'by the book' will usually get you by just fine. But there are factors and effects that are not easily distilled into a book... nor are the authors of said 'book' necessarily concerned with how well a given procedure will work on a 10-year-old vehicle. So long as their advice is effective on a relatively new vehicle using OEM-approved parts... their job is done.


Well, I don't want to bore anyone to death, or attempt to boil down a 1,000 page book into an internet post--but the bottom line is that torque is a rough proxy for bolt tension--very rough...

If you were to take 100 new spark plugs, from the same batch, identical model, same manufacturer into newly-tapped threads, and tighten them with a torque wrench, the actual joint tension would vary by an average of roughly 20-40% based on the literature (and much of the literature isn't even consistent). Of course, that's the average--there would be scatter points with much larger errors. Different manufacturers use different platings on the threads, which confounds things even more.

The big variability is in the coefficient of friction, or nut factor. There are several variables in the spark plug example: thread condition, plating material, underhead smoothness... To give you an idea of the complexities, if you took THE SAME spark plug and threaded it into a new cylinder head 4 times in a row, each time at the same torque reading, do you think the joint would have the same, less or more tension on it by the 4th installation? If you don't know the answeer to that question, how can you say that you're being "precise" by using a torque wrench?

A spark plug installation joint isn't that complex. It needs to be tight enough to withstand cylinder head pressure and engine vibration (so it doesn't pop out), and the forces need to be low enough that you don't hit the yield point of the cylinder head on install or the spark plug on removal (so you don't strip threads or break the spark plug). I think it makes sense to look at each specific joint and determine just what sort of precision is necessary. Since most spark plugs also give angle tightening specs (X turn after seating), I think that's your safest bet.

Lastly, a previous poster mentioned that K varies with lubrication. That's true. However, in general, (and in the field in actual practice), most of the literature on the subject suggests that lubrication also lowers the variability--so as long as you account for the lubrication, your chance of accuracy actually increases with lubrication.

This is a great read on the subject, if you're an insomniac: http://www.amazon.com/Introduction-Design-Behavior-Mechanical-Engineering/dp/0824792971

The more you read, the more you'll realize how little you actually "know".
 
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Very excellent summary of what I also discovered in an internet research of the subject. Here's one guy's take that agrees with your summation:

http://www.algeo.com/~joe/KIAT/kiat_1.htm

He also states that you could have several dozen fasteners from the same lot and they could vary by +/- 30% using the same tools.

"Table 1 gives the Industrial Fastener Institute’s estimate of the effectiveness of various preloading methods.

Preload Measuring Method....... Error
Operator "Feel"................ +/- 35%
Torque Wrench.................. +/- 25%
Angle Torquing................. +/- 15%
Load Indicating Washer......... +/- 10%
Fastener Elongation............ +/- 5%
Strain Gauges.................. +/- 1% "

So many people use torque wrenches blindly, not knowing the principles you so excellently summed up.
 
On a car, all you need is to understand three torque ranges:-

1) Spark plug / Drain plug torque / battery cables:- snug enough so that it will not loosen on its own due to vibration. The fastener is NOT used to put two parts together

2) Lugbolts torque:- fastener is used to hold two parts together and they are supporting the load of the car

3) Something in between e.g. caliper bracket, alternator bracket etc; a part hanging off the car.


Loosely translated, that is about 20 ft-lb, 90 ft-lb and 50 ft-lb give or take 30%.

If you can torque in that range by feel, you should be fine.

You certainly should use torque range where multiple fasteners need to match each other.

- Vikas
 
From AC Delco:
Quote:
Do not use any type of anti-seize compound on spark plug threads. Doing this will decrease the amount of friction between the threads. The result of the lowered friction is that when the spark plug is torqued to the proper specification, the spark plug is turned too far into the cylinder head. This increases the likelihood of pulling or stripping the threads in the cylinder head. Over-tightening of a spark plug can cause stretching of the spark plug shell and could allow blowby to pass through the gasket seal between the shell and insulator. Over-tightening also results in extremely difficult removal.

From Autolite:
Quote:
We do not recommend the use of any anti seize products for installing spark plugs. Antiseize compounds are typically composed of metallic, electrically conductive ingredients. If antiseize compounds come in contact with the core nose of the plugs, it can lead to a misfire condition. Antiseize compounds can also have a torque multiplying effect when installing plugs. This can lead to thread distortion and thread galling resulting in cylinder head damage. Autolite spark plugs are nickel plated to resist the effects of corrosion and seizing. However, plug seizure is aggravated further when steel plugs are installed into aluminum cylinder heads for a long period of time. You may want to consider the periodic inspection of the plugs to reduce the likelihood of plug seizure during extended plug service intervals.

From NGK:
Quote:
Torque is one of the most critical aspects of spark plug installation. Torque directly affects the spark plugs' ability to transfer heat out of the combustion chamber. A spark plug that is under-torqued will not be fully seated on the cylinder head, hence heat transfer will be slowed. This will tend to elevate combustion chamber temperatures to unsafe levels, and pre-ignition and detonation will usually follow. Serious engine damage is not far behind. An over-torqued spark plug can suffer from severe stress to the Metal Shell which in turn can distort the spark plug's inner gas seals or even cause a hairline fracture to the spark plug's insulator...in either case, heat transfer can again be slowed and the above mentioned conditions can occur. The spark plug holes must always be cleaned prior to installation, otherwise you may be torquing against dirt or debris and the spark plug may actually end up under-torqued, even though your torque wrench says otherwise. Of course, you should only install spark plugs in a cool engine, because metal expands when it's hot and installation may prove difficult.

Here again is the NGK technical bulletin advising not to use anti-seize.

http://www.ngkplugpro.ca/content/contentfiles/pdf/NGKSP-0907-1R-Anti-SeizeonSparkPlugs.pdf

From Champion:
Quote:
Champion recommends that you do not use an anti-seize compound, since one has already been applied to the plugs at the factory.

http://forums.pelicanparts.com/porsche-911-technical-forum/475238-anti-seize-spark-plugs-2.html
 
Quote:
However, plug seizure is aggravated further when steel plugs are installed into aluminum cylinder heads for a long period of time. You may want to consider the periodic inspection of the plugs to reduce the likelihood of plug seizure during extended plug service intervals.



I don't want to do this on a Ford 5.4 that lives in the salt belt. In 35 yrs of using just a little i have never had one strip,blow out,or anything else.
The main issue is folks strong arming the plugs when the threads are lubed.
 
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it never ceases to amaze me here. You guys really think the manufacturers don't know they have dissimilar metals involved?

If you read most shop manuals they do not recommend anti sieze.

It's already there. Thanks to the previous poster.

But a dab of it won't kill ya!
 
i used anti-sieze and when I went to remove the plugs I was scared to death that the threads were ruined!! it was EXTREMELY hard to remove the plugs---why? the anti-seize had hardened like thread locker!! I guess I should have used the copper or used less, it was rock hard!!!
 
Originally Posted By: firefighter
Anti seize on plugs? NO. All your silver plugs have a coating on them, no need if you use the correct plug. I have done so mnay plugs at work my head spins, I have taken them out at 100K and have never had one stick. The OE doesnt do it and neither should you. The anti seize can mess with the grounding of the plug and you do not get proper heat transfer. The only time I have problems with plugs is when some one overtightened them and the threads in the head rolled slightly, then the plug galls on the way out, all the anti seize in the world won't help in that situation.


This is one reason I'm considering pulling my new plugs and cleaning off the anti-seize. Thanks.
 
Funny thing is though whenever a manufacturer has a issue with the things not coming out they issue something like this...

ONCE THE SPARK PLUGS HAVE ALL BEEN REMOVED, NEW PLUGS SHOULD BE
INSTALLED USING A FILM COATING OF
MOTORCRAFT HIGH TEMPERATURE NICKEL ANTI-SEIZE LUBRICANT
DO NOT COAT THE ELECTRODE STRAP OR THE PLUG WILL MISFIRE.

Porsche had a similar one for the 930 when they first came out and the threads came out with the plugs,they even made a special repair sleeve for it,i know my engine had two in it.

Ford Kent motors are notorious,if you don't use anti seize and leave them in 50k guaranteed you will be pulling the head.
Ford even recommends pulling them and putting anti seize on them (only after they pulled thousands of heads under warrany).

To each his own.I will keep using it as always.
 
So what matters is who's paying to fix the damaged threads! If someone else is paying then don't use anti seize. If you're paying then do.

Torque is the only non lame reason in mva's post to avoid anti seize. If torque is the only way you know to tighten spark plugs then don't use it.
 
Originally Posted By: doitmyself
Very excellent summary of what I also discovered in an internet research of the subject. Here's one guy's take that agrees with your summation:

http://www.algeo.com/~joe/KIAT/kiat_1.htm

He also states that you could have several dozen fasteners from the same lot and they could vary by +/- 30% using the same tools.

"Table 1 gives the Industrial Fastener Institute’s estimate of the effectiveness of various preloading methods.

Preload Measuring Method....... Error
Operator "Feel"................ +/- 35%
Torque Wrench.................. +/- 25%
Angle Torquing................. +/- 15%
Load Indicating Washer......... +/- 10%
Fastener Elongation............ +/- 5%
Strain Gauges.................. +/- 1% "

So many people use torque wrenches blindly, not knowing the principles you so excellently summed up.


This confirms what I stated in my previous post, and why I torque plugs by angle instead of with a torque wrench.
 
Originally Posted By: severach
So what matters is who's paying to fix the damaged threads! If someone else is paying then don't use anti seize. If you're paying then do.

Torque is the only non lame reason in mva's post to avoid anti seize. If torque is the only way you know to tighten spark plugs then don't use it.


My take on this whole debate boils down to this…

*Manufacturers install the plugs OEM dry, this save a lot of money over time/units produced and satisfies the needs of units sold in most areas of the country.

*Torque specs listing in manuals is for the most part for dry threads and after market packaging usually uses ¼ turn after seated based on these specs.

*There is a coating on the plugs to provide some level of protection from seizing in
most operating conditions.

The issue here is liability.
The manufacturers and aftermarket assume and I believe correctly that the plugs are for the most part being changed by DIY users without access to Factory manuals, TSB’s or torque tools.

If the manufacturer or after market advocated the use of anti seize the door of liability is wide open for the following reasons.

*They have no control over the type or quality of the product being used.

*How the product was applied and in what amount.

*How the DIY regulated the torque as not to strip or damage the threads.
This would be especially dangerous for the aftermarket +1/4 turn.

The following scenario is very possible.
Joe DIY buys 6 plugs, lathers them up good with some anti seize of the counter at the local parts store, goes home and puts them in +1/4 turn and strips one or has a terrible misfire because he got it all over the ground strap.
Joe takes the plugs back claiming defective merchandise or the instructions given damaged his threads.

It is easier and safer for all concerned to simply say install dry.
Chances are good that there will be no issues removing them and if there is the car will most likely be out of warranty anyway.

Liability issues avoided.

In the early 90’s some Honda motorcycles had issues and in the owners manual it specified using motor oil on the threads until the machine could be brought into the dealer and torqued properly with a little anti seize on them for good measure.

This proves to me anyway that when these issues arise they have no problem specifying the use of anti seize when it could cost them money.

Champion actually offers a ceramic based anti seize specifically for spark plugs used in aviation engines, the reason being IMO is that they know that it will be used by a professional and not a DIY.
 
Originally Posted By: Trav
Funny thing is though whenever a manufacturer has a issue with the things not coming out they issue something like this...

ONCE THE SPARK PLUGS HAVE ALL BEEN REMOVED, NEW PLUGS SHOULD BE
INSTALLED USING A FILM COATING OF
MOTORCRAFT HIGH TEMPERATURE NICKEL ANTI-SEIZE LUBRICANT
DO NOT COAT THE ELECTRODE STRAP OR THE PLUG WILL MISFIRE.

Ford Kent motors are notorious,if you don't use anti seize and leave them in 50k guaranteed you will be pulling the head.
Ford even recommends pulling them and putting anti seize on them (only after they pulled thousands of heads under warrany).

To each his own.I will keep using it as always.

Ahhh, the Ford 3 Valve TSB for removing and replacing the 2-piece spark plugs. I've read many horror stories about this one.
 
Just to confound everything here, my Caravan Factory Service Manual says this about installing the recommended Champion or NGK plugs:

(1)Coat threads of spark plug with anti-seize. Be sure not to get anti-seize ANYWHERE BUT ON THE THREADS OF THE SPARK PLUG as
shown in (Fig. 13).
(2) To avoid cross threading, start the spark plug into the cylinder head by hand.
(3) Tighten spark plugs to 17.5 N·m (13 ft. lbs.) torque.

Of course, this is Chrysler, so what could anyone expect?

And, read the box....My NGK's says gasket type plugs should be tightened 1/2 to 2/3 turn past hand tight and 1/16 to 1/8 turn for taper seat plugs. Nothing close to the 1/4 turn mentioned above.
 
I got the 1/4 turn number from some old autolite and boxes.I don't read the boxes much any more so you your information is probably more accurate,i should have used x part of a turn.
 
Old thread, but the benefits of anti-seize on plugs far outweighs the warnings or drawbacks. A stuck plug is a nightmare and potentially serious disaster. Some plugs are already a real challenge and bear to even get to. The worst ones are at really bad angles, small spaces, etc. (back of the engine on a FWD, or up thru the wheelwell, etc.) that do not allow proper direct even pressure and require multiple extensions and pivoting elbows, etc. There's already an added risk of busting one of those even if it's not stuck simply due to the difficulty accessing it.

Breaking a plug in the engine is going to be a very challenging and possibly expensive lesson on not using anti-seize. Could be hundreds of dollars, and hours of work, type of a lesson. And on all my plug removals I hit it with some liquid wrench and let it sit before even attempting to remove.
 
Old thread, but the benefits of anti-seize on plugs far outweighs the warnings or drawbacks. A stuck plug is a nightmare and potentially serious disaster. Some plugs are already a real challenge and bear to even get to. The worst ones are at really bad angles, small spaces, etc. (back of the engine on a FWD, or up thru the wheelwell, etc.) that do not allow proper direct even pressure and require multiple extensions and pivoting elbows, etc. There's already an added risk of busting one of those even if it's not stuck simply due to the difficulty accessing it.

Breaking a plug in the engine is going to be a very challenging and possibly expensive lesson on not using anti-seize. Could be hundreds of dollars, and hours of work, type of a lesson. And on all my plug removals I hit it with some liquid wrench and let it sit before even attempting to remove.
I think that was covered pretty well 11 years ago.
 
it never ceases to amaze me here. You guys really think the manufacturers don't know they have dissimilar metals involved?

If you read most shop manuals they do not recommend anti sieze.

It's already there. Thanks to the previous poster.

But a dab of it won't kill ya!
True- but some manufacturers do recommend its use. My Honda Accord V6 FSM says to apply some to the threads and torque to 13 #. I saw traces of AZ on the threads when I replaced the factory originals. I use it but reduce torque. As you say, "a dab of it wont kill ya".

I even use it on lug nuts (gasp) but the manufacturer actually recommends that.
 
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