Spark plug torque: no more +/-?

[IndyIan]

I would say never do hand tight plus a set fraction of a turn. You are relying on the profile shape and hardness of a $.005 washer to be consistent. I got almost burned on that, with following the directions even though the felt too loose... and they were loose, but I heard the first loose plug in time...
I had old snowmobiles as a kid so I've done 100's of plugs in aluminum heads without stripping one, or having one come loose and reused plugs with old washers a few times each.
IMO the best way is to tighten holding on to socket wrench with your hand on the head and feel the washer get squished down, and then you'll feel the washer squish and bottom, and then apply your spec torque, or go by feel with one finger on the socket handle.

 

[drtyler]

I don't know. I think everybody is citing the same source whatever it is.

I believe it is supposed to be +/- as usual, but the - is getting left off due to ignorance or laziness.

 

[vavavroom]

I believe it is supposed to be +/- as usual, but the - is getting left off due to ignorance or laziness.

Possibly. Hence my original question whether or not there was a new way of stating a torque spec and tolerance.

Beru says 15 to 30Nm. That's the range for the soark plug but not necessarily for the bead.

 

[JHZR2]

This has been the case of every NGK plug I've installed over the last decade or more. I like it because it takes all the mystery out. The only caveat is that the recommended torque angles are for brand new plugs with the crushable washer.

Scott


View attachment 226316

Takes the mystery out? I don’t get why they don’t just say 1/4 past finger tight or something. Why it has two stages.

Unnecessarily complex imo…

 

[slo town]

Takes the mystery out? I don’t get why they don’t just say 1/4 past finger tight or something. Why it has two stages.

Unnecessarily complex imo…

They're not saying it's done in two stages, unless you consider tightening it to finger tight stage one. All they're saying is to tighten it anywhere from 1/2 to 2/3 of a turn once past finger tight. NGK is giving a range. Doing it this way doesn't even require a torque wrench and/or whether or not the threads have been lubed makes no difference.

The only gap in the NGK instructions is that some dim wit might re-torque a previously installed plug that has a compressed crush washer, which means they'd over torque it - by a lot. But IMO that's more of a case of someone not knowing how stuff works.

I'm not suggesting that's you either. Based on your posts it seems like your mechanical background and experience is extensive.

Scott

 

[JeffKeryk]

I enjoy using the SO torque wrench, but even that assumes proper use. I am not too proud to say I could still make a mistake even with a quality tool. I just aim for the low end because I always use a little you-know-what.

 

[Exhaustgases]

How would you check the final torque? Outside of high precision tools and factories, the end user has no way to verify the final torque of a fastener. Therefore a range is effectively useless.

I have a way to check it, so all is cool my way.

 

[ARCOgraphite]

They don't want you to use your calibrated elbow unless it's accurate to within the stated tolerance, of course.

I used one of these and my car wouldn't start later

 

[vavavroom]

How would you check the final torque? Outside of high precision tools and factories, the end user has no way to verify the final torque of a fastener. Therefore a range is effectively useless.

Tolerances ensure "within spec." Some things require tighter tolerances than others. Stating tolerances makes perfect sense to me mostly because it is an indication of how critical the stated value is. Obviously, in the case of spark plugs, the tolerances are rather large. Just look at what BERU publish.

The thread has veered from its intended topic. My question is not about how critical torque is, if you even need a torque wrench, how to use a torque, or what color the torque wrench is.

 

[KrisZ]

Tolerances ensure "within spec." Some things require tighter tolerances than others. Stating tolerances makes perfect sense to me mostly because it is an indication of how critical the stated value is. Obviously, in the case of spark plugs, the tolerances are rather large. Just look at what BERU publish.

unless you own any of these torque testers or a high precision torque wrench that displays the actual torque value, you have no way of verifying your final torque. You set your clicker to the nominal value and torque until it clicks.

A range is essentially useless for an average mechanic or DIYer. The tolerances are mainly for the factory where the tools record the torque values at each operation which is stored in the manufacturing software program, which then either gives a green light or flags that operation station if the values falls outside the range.


https://www.checkline.com/torque_testers

 

[Lubener]

I never used a torque wrench for spark plugs. When you have changed so many for many years, you develop a "feel" for the proper torque for the type of plug being installed.

. Newbies are more likely to use a torque wrench for plugs.