Sparking plug torque

[abstamaria]

I have always used 25 lbs as the manual suggests. This always seemed higher to me than common practice, particularly for aluminum heads (finger-tight then snug up 1/2turn). I was wondering if there was new consensus here?

I do note that NGK recommends 25lbs too. I have always used copaslip, but note also that current thinking suggests that plugs be installed dry (spark plug manufacturers seem to support this). In any case, a lubricated plug should be torqued to a lower value. If so, what value have you been using?

By the way, NGK suggests one use the standard torque settings for cool engines only.

Andy

[lotocone]

Andy,

I went with 20 lb. ft. when installing some spark plugs today. This is within the range of 19-22 that Brian Buckland recommends in his book (p. 503).

The NGK spark plug box I have shows 18-21 lb ft. for 14 mm gasket type plugs used in aluminum heads.

Hope this helps,

Bob

[lotocone]

Forgot to mention in my post that I used a little Copaslip. Lubricant was not mentioned by Buckland or the NGK info I have.

[abstamaria]

Thanks, Bob. I'll use 20 then, but probably without Copaslip this time.

Andy

[reb53]

but probably without Copaslip this time.

Andy

Maybe not a good idea.
I've had plugs that have been in a while that were reluctant to come out.
Had to use the old "in a bit, out a bit" technique to remove them. Plus a squirt of penetrating oil once there was bit of a gap.
Now use a smidgeon of "never seize" to stop the reaction between the head and plug.
( Which one would assume the plug makers had sorted but don't seem to have).

Even dry 25lbs seemed high to me so go by feel, probably 15 to 20.
Plugs are like wheel studs. OK for a mechanic to over do because the results won't come back to haunt him, just some poor guy down the line.

Cheers,
Ralph.

[abstamaria]

??
I once followed discussions on several sites on whether to use anti-seize or lubricants on spark plugs and came away with the conclusion that I shouldn't apply any. Here is a note from NGK, advising AGAINST using anti-seize and lubricants.
?
http://www.ngksparkplugs.com/pdf/TB-063 ... isieze.pdf

Now, this goes against my long-standing practice, but I recall having read similar positions taken by other plug manufacturers. Note that this is for plated plugs such as NGK.

BTW, If you lubricate the threads, you should decrease the torque setting. The Bosch and similar mrchanic's handbooks will tell you by how much. Most torque specs are for dry threads.

I will pull the plugs from my TC after a long period of storage. I hope they come out easily (I probably put copaslip when I installed them). I still have to decide whether to follow NGK's advice although that seems the smart thing to do.

Andy
?

[abstamaria]

To add to the confusion, Champion sells anti seize for it's plugs (graphite based seems usual for spark plugs). This thread might be interesting
http://bmwmotorcycletech.info/sparkplugs.htm

[rgh0]

I use the recommended 24 to 28 ft lbs in the Lotus manual ( nominal setting of 25 ft lbs on my torque wrench). This produces the recommended 1/2 to 2/3 of a turn after finger tight that comes on the box of the NGK plugs I use.

Note you can only use this 1/2 to 2/3 of a turn guide for a new plug as a used plug sealing washer takes a set and requires less of a turn to achieve the same seating pressure when reinstalled so I go by torque only when installing a used plug

I used to do the plugs assembly with dry threads for many years but after a couple of occassions having the threads sieze in my racing engines I resorted some years ago to using antisieze. I personally use the Loctite nickel antisieze. It made no signficant difference in amount of turn to achieve the set torque with dry versus lubricated threads and i have had no thread sieze problem since.

Never had a thread sieze on my road plus 2 twin cam but then I change plugs on this a lot less frequently and its operating combustion temperaures are much lower !!! However I now put antisieze on all the plugs I fit in any engine as its a real pain to slowly extract a semi siezed plug as described and pray you dont strip the threads

cheers
Rohan

cheers
Rohan

[abstamaria]

I'm inclined to put copaslip, bu here is a lift from a BMW forum:
-
"Here's what Autolite says about using anti-seize (snicked off the net somewhere):

We do not recommend the use of any anti seize products for installing spark plugs. Anti seize compounds are typically composed of metallic,
electrically conductive ingredients. If anti seize compounds come in
contact with the core nose of the plugs, it can lead to a misfire condition.
Anti seize 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.

Here's what AC/Delco says:

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.?


heres the Pelican Parts explanation
" Install each plug into the cylinder heads without using any anti-seize compound. Torque the spark plugs to 25 Nm (18.4 ft-lbs). While writing "How to Rebuild and Modify Porsche 911 Engines", I discovered that Porsche doesn?t recommend the use of anti-seize compound, as detailed in Porsche Technical Bulletin 9102, Group 2, identifier 2870. The bulletin applies retroactively to all Porsche models and the theory is that the anti-seize tends to act as an electrical insulator between the plug and the cylinder head. This could have detrimental effect on the firing of the spark due to the loss of a good, consistent ground connection. Keeping those findings in mind, I would make the same recommendations for the BMW cars."


looks like clean and dry is the way to go

[Andy8421]

As ever, the advice is contradictory.

It can't be both:

"Anti seize compounds are typically composed of metallic, electrically conductive ingredients. If anti seize compounds come in contact with the core nose of the plugs, it can lead to a misfire condition." (Autolite)

and:

"anti-seize tends to act as an electrical insulator between the plug and the cylinder head. This could have detrimental effect on the firing of the spark due to the loss of a good, consistent ground connection." (Porsche)

Corrosion, siezed plugs and resultant thread damage in ally heads is a real risk. The arguments for not using anti sieze - it may or may not conduct electricity, you may smear it over the insulator or you may damage the thread with over zealous tightening can all be overcome with a bit of care and attention when fitting the plug. Corrosion due to dissimilar metals in the plug body and head cannot.

I would suggest a good quality graphite based grease or copaslip is probably the way to go.

[Galwaylotus]

I always use anti-seize on plug threads and have never had an issue either with stripped threads or misfiring due to any insulating effect. As mentioned above, the important factor is care of installation.

[ricarbo]

I must admit i always sprinkle a little graphite powder (the sort locksmiths sell) on the threaded part of a new plug, not allowing it to get on the insulator where it could cause tracking. If an old plug is being refitted, i don't bother. I find the plugs screw in easily by hand, making it easy to avoid cross threading. then i just nip it up with a spark plug spanner. Haven't had a problem yet.
Richard

[S2Jay]

In the NGK bulletin, they refer to the potential to ?over-tighten? because the anti-seize ?allows the installer to mistakenly over-tighten the spark plug?. Use of A-S produces a different feeling to the installer.

I suspect that their concern is more with the overzealous semi-professional who may be in a rush, or who may not be quite as conscientious as would the actual owner/mechanic of his/her own classic vehicle.

How hard does one need to torque a new plug in order to actually break the thing at the threads? I suspect that this concern is largely misplaced with a group of DIY vintage car owners such as this. For someone who may not change plugs frequently, or who may not start or drive often, the long term protection of the A-S likely far outweighs the possibility of tightening so much as to break a plug. Just another 2c.

Jay
26/5009

[types26/36]

.....using a torque wench to fit plugs (shaking head).....never have and never will .....OK! .....Yes..I know its in the manual..... Yar-de -Yar-de Yar.... what's wrong with you people ....don't you have sense of feel....flame away

[UAB807F]

.....using a torque wench to fit plugs (shaking head).....never have and never will .....OK! .....Yes..I know its in the manual..... Yar-de -Yar-de Yar.... what's wrong with you people ....don't you have sense of feel....flame away

don't worry, you're not alone.

I've got one of those T-bar flexible socket wrench things (2 in fact, one for smaller plugs) and I've only ever used wrist pressure on the T to tighten up plugs. I'm sure it's not right by the book or the spark plug manufacturers but it seems to work. I hold my hands up & say the only thing I religiously follow torque settings for are bearing shells & cylinder heads. The rest just go by what I feel is right. (although I admit I do look to see what it's supposed to be - light touch, moderate pull or scaffold pipe & heave tightness )