Spark Plug Question

13ft.lbs. might be right - but it does sound a little low, personally. That might be the torque on the coil on plug igniter bolt, as that doesn't need a lot of torque to be secured.

Reason they list a range of torque ratings, depends on what sort of contamination there is on the treads of the cylinder head + that coating that they add to the threads from the manufacturer.

Most of the plugs I run across have an integral washer built in - you tighten the plug until it makes contact with the cylinder head (finger tight) - then finish with whatever the manufacturer lists on the box, ie. an extra 1/3 to 2/3 turns more. Even ones without the washer (taper seat) usually get an additional 1/16-1/8 of a turn.

You can verify with a torque wrench afterwards, if you feel like it. This is one of those things that you develop a "feel" for as you do them. The more you do these of things, the better you get estimating the amount of torque you are applying with your hands.

Myself - I've gotten pretty lazy with the plugs - I don't even use my torque wrench on those anymore.

I think the torque values are listed somewhere on the forum. I don't have ready electronic access to my FSM or ECP like before, so I can't easily pull those numbers up (ie, hardcopy lookup).

Like I mentioned, just go with the tightening scheme that the plugs recommend. Most common torque wrenches won't have the accuracy to pick up on those low torque values anyways. You need one that reads from inch pounds to 10s of lb pounds - those are unfortunately extremely expensive if new. Pretty hard to find second hand.

That's why they list the tightening scheme on the package, as most DIYers won't likely have tools with that sort of accuracy.

^^^ What dom said. That torque wrench is more of a general purpose use. I wouldn't use it for tightening plugs. Being a 1/2 drive - that wrench is likely 20" long or so, you could easily overtorque those plugs in a heartbeat.

If you've played with your torque wrench, you should notice that even when it hits the indicated torque, you could still continue to tighten the nut/bolt. Most torque wrenches are most accurate in the middle of their torque range. The old engineering rule of 80/20 is a safe assumption when working with unknown calibration of the tool. Example - a torque wrench with a range of 20-150ft.lbs - might only accurately work in 80% of its full range. That means it might only be accurate from 33-137ft.lbs. At the extremes, it might read accurately or it could be off a couple of ft.lbs. In the case of sparkplugs - a couple of ft.lbs + error introduced by the operator (ie, over-tightening) + any lubrication on the threads (drops apparent torque) - that could be way too much.

If this was the old copper plugs. which need to be changed out every 10K miles - I'd probably invest in a smaller torque wrench. But since these iridium plugs have up to 120K mile lifespan (OEM plugs) - just tighten them according to the directions.

Perfect for lugnuts.

Yes, 76ft.lbs. should be fine for lugs For suspension work, most should be covered with that 1/2" torque wrench you already have.

3/8" torque wrench, even at 10ft.lbs, probably still not sensitive enough to use for plugs or other low torque rating. Most don't need that sort of wrench unless you want to get into rebuilding transaxles/transmission (ie, bearing preloads, where torque is in the 10's of in-lbs.)

Just go by the box - usually ends up working the best anyways.