Spark Plug Gap and Torque

The numbers come from the Toyota factory repair manual, and you can confirm that by subscribing to techinfo.toyota.com

The actual gap spec is 1.0 to 1.1 mm and I adjust the new iridium spark plugs to 1.0 mm. Do not adjust the gap on a used iridium plug.

My 3/8" torque wrench is a Craftsman model calibrated in in.-lb values. 13 ft.-lb is 156 in.-lb.

 

Just to open up the can of worms: any opinions on anti-seize? FWIW, when I took a look at ours I went with HINT of anti-seize, and 13 ft-lb.

Also, I believe most of these spark plugs, especially high-end iridiums, are pre-gapped. And some manufactures caution to not try to adjust the gap. Bottom line, it's not mandatory to re-gap them.

I picked up a cheap, made-in-China 3/8" torque wrench with markings down to 5 ft-lb. Did a funky test of it and my other 1/2" drive torque wrench, setting both to around 30 ft-lb and torqueing on a lug nut (on the car, already torqued to higher value) with a digital pull-scale, one foot from center. The gave very similar, and accurate numbers, so I think they're both close.

You should check what socket size you need too. On 3rd gen it's 9/16" for example, very small.

 

With anti-seize lube, the less used the better. I believe that NGK does not require anti-seize lube to be used on its plugs. I also use just a tiny amount of lube on the spark plug threads.

 

I used a small amount of anti-seize. That was the consensus of the mechanics at work.

 

I put on a slight, uniform amount, then wipe it off with a rag. That way you end up with just a little residual in the grooves of the threads.

3rd gen Repair Manual says 15 ft-lb with dry threads, so I figure 13 with that slight amount of anti-seize is about right.

 

Anti Seize every time. I had an aluminum block Nissan truck and never used it. One plug fused to the aluminum and it had to have a helicoil put in. I have used anti seize on every eng. for plugs and have never had an issue. If someone tells you not to use it they don't know what they are talking about. From what I have read, its over tightening. I never have used a torque wrench on spark plugs in all the years I have been installing them, from my cast iron engs of the 70s to my aluminum bike engs of the 80s to my aluminum ones of today. Its like tightening down a new toilet. You snug it up but not hard. Its a feel thing. I guess if someone is not used to doing it they may need a torque wrench.

 

The indium plugs are good for 150+ thousand miles, changing the plugs once will get you over to 300k miles. You'll never take them out again.

Ngk and Denso does not recommend using antiseize with their plugs

 

That's what I read in Denso manual. Antiseize have a torque multiplying effect when installing plugs.
If using anti-seize compound, use sparingly and reduce torque by 30%

 

I am replacing my plugs with Denso iridium plugs for my 120,000 mile service and Densos' website says no anti seize! I think using some sparingly, like wiping off the excess and less torque, sounds like the consensus?

 

If the Denso website says to not use anti seize, then why use any?

 

I'm torn, lol.

 

I used anti seize the first time I replaced plugs. This second time I didn't use anything. I don't even torque them down...just tighten until the crush washer stops flattening.

 

Well gang I'm going to go out on a limb, and be a little embarrassed. As a rocket engine guy I should know better and as a very much custom car builder I should really act better, however both of our Priuses are right now getting their FIRST spark plug changes at 285,000 miles. It sounds nuts but since I was getting 47 miles a gallon average, driving 100 miles a day all these years and my wife doing the same, then why mess with it. LOL LOL, send all the ridicule and jokes.

Needless to say they're getting their first gas struts and spring tower replacements, valve cover gaskets, PCV valve, and the list goes on evaporator core, expansion valve, new compressor oil ... I tell everyone for the last 14 years you just can't beat these cars. An 06' and 08'

All I need now is a nice tan carpet kit for one car and possible second rebuilt battery from Houston for one car which I've been replacing cells in every year for the last 2 years. That car's replacement battery was only $1,000 6 years ago so well worth it.

Doing the math savings on maintenance and gasoline savings over our prior 20 mile per gallon Volvos, both of these cars paid for themselves. So, we drove them for free. Bamb!

Posted via the PriusChat mobile app.

 

I don't understand why don't all manufactures recommend anti-seize, it makes so much sense using it.

 

I don't understand why don't all manufactures recommend anti-seize, it makes so much sense using it.

Most people will only do a couple dozen spark plugs during their entire life. The manufacturers engineer, design and test hundreds of various models of spark plugs. It's probably safe to assume they know what they're talking about.

But, for some things to think about....

Many anti-seize compounds are electrically conductive, there's always the chance someone will glob it onto the electrodes

Will some anti-seize compounds create heat dissipation problems? The heat of a plug is dissipated through the threads and into the head.

You think you put the anti-seize onto the threads sparingly, but when you install the plug, much of it's pushed out and goops around the top of the threaded area. Next time you change the plugs, where does the old AS go? Does it stay in the plug tube and then get stuck on the electrode of the new plug as it's lowered into the hole?

And then we think....people can't possibly mess up putting on a little bit of anti-seize...and what can I say? There are people in the world who can break an anvil using a rubber hammer if given the chance.