Which is more important when changing spark plugs

[njohnson]

Hi everyone,

I have a question, which is more important when changing spark plugs, following the torque setting or the 1/2 to 2/3 turn?

I am changing the spark plugs on our SUV. I bought NGK spark plugs to put in. On the NGK box, it says 1-2 to 2/3 turn. I have a Chilton manual for the SUV, and I looked it up, it says to use 13 lbs/ft to tighten the plugs.
I read on NGK's and Denso website that the use of anti-seize or grease is not recommended because it lubes the threads and when following the correct torque setting, the spark plug can be overtightened.

I did not use any anti-seize on the new plugs, I used the plug socket and extension, threaded it by hand until tight, then used the torque wrench to 13 lbs/ft. It was a little hard to judge because I couldn't turn the wrench in a nice, clean 1/2 turn because of the components around the engine in the way, but I was able to do 1/4 or 1/3 turns of the torque wrench. I tightened to 13 lbs/ft, I did the first two on the driver's side, and was on the third plug. After looking at the threads of the old plug, I started thinking. Yes, I was not putting any anti-seize on the new plugs, but, I had put them on the last set. I started wondering if there was enough anti-seize left in the threads inside of the engine to affect the new plugs.

The NGK website was saying that anti-seize could affect the torque by up to 20%. Reducing the 13 lbs/ft by 20% left me with 10.4, so, I set the torque to 10 lbs/ft, and tightened down the third new plug.
Wondering about the other two I had just done, I went back, loosened them back up, tighten by hand, then torqued them to 10 lbs/ft.

The reason I asking about what to follow, the torque setting or the 1/2 to 2/3 turn, is because of the second plug.
The first plug I loosened back up and retightened seemed fine. With the 10 lbs/ft setting, it tightened roughly about 1/2 turn.
The second plug I loosened, tighten by hand, but, using the torque wrench, it only went about 1/4 turn before it was clicking. Loosened it back up, and did it again, same thing.
Why is it only going about 1/4 turn before it clicks? When the other two were roughly 1/2 turn?

Something going on with the plug? Or threads in the engine?

Now I am concerned about the second plug, I don't want it to be under tightened, but, I don't want to over tighten it either.

I read the cleanliness of the threads can also affect the torque setting, makes sense, any kind of crud or build up would cause more resistance to turn, possibly reaching the amount of torque, causing the wrench to trip, before the plug was fully tightened. Judging by the way I could thread it by hand, the threads seem pretty clean, I think.

So, what do I follow? Torque setting? 1/2 to 2/3 turn?


Thanks,

 

[Doc8404]

I go by torque if I can.
And ensure you research any updates.
My truck now recommends nearly double what it once was.

 

[NibbanaBanana]

I go by torque spec and reduce by 20% if using anti seize. Never had a problem.

 

[The_Eric]

I like going by the amount of rotation. Then torque (and lubrication) doesn't come into play. Rotation allows a fixed amount crush on the metal gasket that is installed on the plug. There is some leeway too- if tension suddenly comes up at 1/2 turn, then no need to continue to try and achieve 2/3.

 

[Ethan1]

I'm a stickler for using torque wrenches, but I do spark plugs by hand. I've never had a problem

 

[mk378]

The 1/2 to 2/3 turn is only for the first time installing a new plug. When you put a plug back that has been previously tightened into an engine, its gasket is already crushed, it will only turn about 1/4 turn.

 

[kschachn]

Originally Posted By: The_Eric
I like going by the amount of rotation. Then torque (and lubrication) doesn't come into play. Rotation allows a fixed amount crush on the metal gasket that is installed on the plug. There is some leeway too- if tension suddenly comes up at 1/2 turn, then no need to continue to try and achieve 2/3.


Yes, and at least on the NGK boxes there is a chart showing the correct angle.

 

[Drew99GT]

Yea, I've found on some cars that carbon in the threads can greatly affect spark plug installation; therefore, I always go by hand/rotation. On my Corolla, it gets carboned up so bad that sometimes the plug feels tight with only 1/4 rotation, but when I use a spark plug thread cleaner, it will go 1/2 turn. For some reason the 3rd cylinder is really bad.

 

[bunnspecial]

I'm a torque wrench stickler whenever possible, but I go by turns on the plug also.

An old mechanic advised me when installing spark plugs to use my left hand(or I should say non-dominant) on the socket wrench and choke up nearly to the head of the wrench. Doing this, I can feel the washer crushing and I stop when I feel the resistance rise. Of course, on used plugs, I just use my "left hand torque wrench" and tighten until snug.

 

[bubbatime]

I use a calibrated bubbatime torque wrench called my hand. The spec is "good-n-tight".

Ive changed hundreds/thousands of plugs and have never had an issue yet.

Also, 13 ft lbs is a pretty low figure. You have to use a pretty specific (smaller) torque wrench to get an accurate reading that low. You dont want to use a 1/2 drive, up to 150 ft lb torque wrench for such a low figure.

 

[Kestas]

Originally Posted By: Ethan1
I'm a stickler for using torque wrenches, but I do spark plugs by hand. I've never had a problem

Same here. I insist on using a good coating of antiseize on the threads and seat, which leaves torque values unreliable.

 

[Bud_One]

I've always anti seized and hand torqued every spark plug I've ever installed.
Never had an issue ever removing them.
I can't explain the torque to apply, it's just a learned feeling you acquire over years of wrenching.

 

[y_p_w]

Depends. The first time I'd ever done a spark plug install I did the seat and crush where I did it 2/3 a turn. Worked out great. Late on I tried using a torque wrench, especially when just checking plugs for erosion/condition between replacement. The last time while installing some NGK Laser Platinums it was odd because I couldn't seem to get the washer to crush at all. I'm pretty sure I went well beyond the torque specs, and when I pulled them out to check the washers looked brand new. I then just did it "good and tight" until I thought it wasn't going to destroy the coil. It's been at least a couple of years since and I'm sure I didn't destroy the threads and the plugs haven't shot out the tube yet.

 

[wtd]

I always torque by hand and have never had a problem.

Wayne

 

[AntsinmyEyes]

gutentight for me

 

[i_hate_autofraud]

If going into an aluminum cyclinder head, I always use anti-seize paste and reduce torque.

Bone dry threads 5 years later are likely seize, gall and strip-out next time!!

 

[kschachn]

Originally Posted By: i_hate_autofraud
If going into an aluminum cyclinder head, I always use anti-seize paste and reduce torque.

Bone dry threads 5 years later are likely seize, gall and strip-out next time!!


Yeah, I used to think that too until I got my Toyotas. The replacement NGK plugs always said not to use anti-sieze so I never have, and it's been a long time later and they've always come out OK. No seizing, galling nor stripping. Same for my Accord, but those don't go as long as the Toyota ones do.

 

[slacktide_bitog]

A torque wrench is like ten bucks at Harbor Freight, and only five seconds more time to set the torque setting, so there is no reason not to use the torque spec.

And per NGK's bulletin, NO anti-seize

 

[robertcope]

I use a torque wrench and no anti-seize. Never had a problem.

 

[eljefino]

I usually use a stubby ratchet like this

and go "gutentight".