Spark plug torque specs

ford
e250

#1

what is the torque on these spark plugs


#2

Snug


#3

that was really helpful


#4

But true.


#5

#6

I don’t know anyone who uses a torque wrench on spark plugs…


#7

I actually have before. For a long time I just took 'em out and then put 'em back in. Then I once came across the info that plugs did have torque specs. So I figured I had spent $$ to own the dumb torque wrench - I may as well use the dumb thing.

I’m pretty sure I was doing pretty much the same torque before I even know about this. These days I’m older and crankier - so I’m more often thinking taking the torque wrench out is just one more dumb thing to take out and put away.


#8

I don’t know anyone who uses a torque wrench on spark plugs…

Yes you do! I use a torque wrench to install my plugs. I guess we haven’t met in person, so I suppose we don’t know each other very well.

I’ve got the torque wrench, so I figured I might as well use it.


#9

I also use a torque wrench on spark plugs. Too many stories of stripped threads has made me more diligent.

The torque spec should be marked on the sparkplug box, in the repair menual, or on the website for the plug manfacturer.


#10

Often the threads in the head need dressing or the torque readings will be totally incorrect.


#11

Speaking for myself and other mechanics I know, none of us use a torque wrench. Feel is far more trustworthy than an iffy torque wrench (especially if it’s a 1/2" drive at low settings) or a given spec which will vary depending on the source.

One book of mine gives the torque on an aluminum head Ford 4.6 at 7 to 14 Ft. Lbs. Why not throw a grenade at it?
It’s quite possible to pull the threads with either specification, especially on a short reach or shallow thread depth spark plug.

I’ve seen specs for a certain application given as a certain amount in one book, something different in another, still something different on an internet site, etc. so it’s a grab bag anyway of what is allegedly correct anyway.
On one application an 8 pound reading was given and another manual stated 17 Ft. Lbs for the same application. (Ouch on that one.)

If a torque wrench is used it should be an accurate 3/8 or 1/4 drive tool and one should adhere to the low side of the tolerance range.

(Not spark plug related but consider the rocker arm sideplay spec on a Harley Davidson Shovelhead engine. The factory manual gives it as .004 to .025. This also falls into the grenade category.)


#12

I have a torque wrench too…but rarely used…Never had a problem NOT using a torque wrench on sparkplugs…


#13

Ironically, I never started using a torque wrench for plugs until I started hanging out here. Too many scary stories. Too many ham-handed people.


#14

I use one of these to tighten, when it’ll fit.

http://lh3.googleusercontent.com/public/43xyF-NM366kxioNjGNU2VprtO7UpchCHtv9RBC_FrDOrZjLVqdnMoSLcKG5BkK7I9rt1-43b-Hj0bRL131kH7BwCYTxLZpHOkoFte5LOM8it6aLkFRBVhvljfEz7dIN4l0Zlgc497JCv_5BDr9iPoKVGRVxpCJtnEz7MMYzdw

That won’t always break the old one loose, though, so a socket and ratchet may be needed for that. It’s a lot harder to overtighten the plugs with that tool. Just turn it for as long as it turns easily, then turn it a little more.

When I had a plumbing project, a plumber gave me some good advice. He told me I didn’t have to knock it out of the park when tightening a threaded connector. He said to tighten it snug, and turn on the water and see if it leaked. Then tighten as necessary.

I’d advise learning with a torque wrench, and start on the low end of the torque. Pretty soon you just learn how it feels when it’s ready. If the car has exposed plug wires, you can tighten the plugs and run the engine. If you hear a compression leak, or feel it when you hold on the plug wire boot, the plug needs to be tighter. As long as it holds compression, and doesn’t work its way loose with time, it’s tight enough.


#15

I never use a torque wrench for spark plugs. I go by feel.

There are some situations that require the use of extentions and a U-joint in order to gain access to the spark plugs. And anytime a U-joint is used a torque wrench can’t be used because it results in inaccurate torque readings.

Tester


#16

Exactly right. Kind of like losing a little engine oomph when the power train makes a 90 degree turn at the differential.


#17

Tighten them until they get loose, then 1/2 turn more.

Just kidding.

Most professionals have enough “feel” that we don’t use a torque wrench. If you do decide to use a published specification (you don’t give a year or engine size), remember 2 things:

Any torque spec is going to be for clean, dry threads–never use anti-seize on spark plugs.

If your torque wrench has not been calibrated and verified within the last year and properly cared for, don’t bother. No point in using a torque wrench if you don’t know it’s accurate.


#18

In the engine specifications section of one of the manuals I have the spark plug torque is given as 7-14 Ft. Lbs on an aluminum head Ford 4.6.
That’s a lot of lee-way and the thought of applying even 7 Ft. Lbs (assuming the torque wrench is dead on) to things like shallow threads, threads which may be shaky from someone getting hamfisted in the past, etc would make me a bit antsy.

Got to love those guys who believe the proper method of removing and replacing plugs is to zip them out with an air ratchet and then ram the new ones home with the same tool. It does improve the flat rate flag though… :slight_smile:


#19

Snug with a short 3/8" drive ratchet is good for spark plugs. If you do use a torque wrench, use a 3/8" or 1/4" drive tool, NOT a 1/2" drive torque wrench. The given spec will be at the bottom of the torque wrench’s range, which is typically less accurate than the middle of their range. My father likes to use a torque wrench on everything, and he ruined my younger brother’s opinion on them by insisting, against my brother’s will, upon installing spark plugs in his first car using a 1/2" drive torque wrench. After my dad tore the threads out of the first spark plug hole, my brother chased him away from the project and drove the car on three cylinders to a friend of mine’s house, where my friend cut new threads and installed a different spark plug he had laying around with Loctite. For some reason, a Heli-Coil wouldn’t work, he said. Either way, he got my brother’s car running again, but gave him the condition that he never try to change spark plugs again, or at least to never remove the one he installed. My brother drove the car like that for a year before selling it, and has never again allowed a torque wrench to touch spark plugs anywhere near him.


#20

I’ve got a Snap-On stubby 3/8 ratchet about 3" long and that’s what I’ve always used for plug installation. It’s always used with the ratchet head in the palm so as to provide very little leverage.

It’s kind of amazing to me that little ratchet has been with me since back in the 70s sometimes and has never failed, gotten lost, or been misappropriated by someone with sticky fingers.