The only tool you need to tighten your spark plugs properly is your hand. You can’t beat those five digits when it comes to providing an even and consistent compression level on the plug’s gasket sealing surface. But suppose pose you’re concerned about giving optimum thread contact with your plug’s threads (to prevent cross-threading) or about getting some extra clamping force (to increase torque, which in turn assists in drawing the mating surfaces further toge. In that case, you may want to consider using a supplemental wrench for spark plugs.
Always use anti-seize compound on spark plugs
Many folks will also tell you that you should always use anti-seize compound on your spark plugs to protect the threads further and make removal easier down the road. I’m not going to get into the debate about whether or not to use anti-seize, but if you do choose to apply it, be sure to do so sparingly, a little goes a long way. Too much can cause problems of its own.
So, now that we know a bit of torque and how it relates to spark plugs, let’s take a look at how tight they should be torqued. I want to point out that spark plug torque specifications are manufacturer-specific, so you’ll always need to refer to the vehicle’s service manual for proper tightening specs. For reference purposes, though, here are some general guidelines.
How tight should spark plugs be torqued?
- New plugs (not gapped or installed) – 15-foot pounds (20 Nm)
- Most gapped (pre-gap) plugs – 12-foot pounds (15 Nm)
- Pins with damaged threads – 24-foot pounds (30 Nm)
Torqued adequately because they don’t make it past the break-in period anyway. As far as pre-gapped (or “pre-set”) plugs go, the rule of thumb is to tighten them to 12-foot pounds (15 Nm), which is about 75% of the recommended torque value.
Again, always consult your vehicle’s service manual for the specific torque specs that apply to your make and model. And remember, using a supplemental wrench can help you achieve an even more consistent torque level, something that’s especially important when dealing with spark plugs.
How much does a torque wrench for spark plugs cost?
- If you take your car to the dealer, it will be at least $45.00
- Midas charges $30.00
- Pep Boys charges $39.99, The Home Depot charges $15.99
The cheapest of all is Harbor Freight
They have a 2-inch drive click style for only $8.99, but of course, I’ve never used one, so I can’t recommend it! You use a torque wrench to tighten nuts and bolts, so why would you need another kind of tool to tighten a tiny little bolt on your spark plug? Because with larger diameter bolts, you only need a few degrees’ difference between what the bolt is designed to hold and what it will strip out. With spark plugs, you need half or less of that difference.
If your torque wrench didn’t come with a scale for measuring “inch-pounds” (you’ll want one if not), see my article on how inch-pounds work.
Other tools you may find useful
My other favorite tool besides a torque wrench is a “depth gauge,” which can measure from the top of the plug down to the top of the insulator. It’s convenient for checking aftermarket plugs because it will tell you when they bottom out against the head and thus are fully seated in heat transfer resistance to the metalhead. Still, it also means you when they’re too deep into their cylinder. If they bottom out more than 0.020″ below the surface of the head, you should back them out and re-gap them.
If you’re looking for a torque wrench that is specifically designed for use on spark plugs, there are a few different options to choose from. You can go with a standard 2-inch drive wrench, or if your vehicle has suitable deep sockets, you might want to consider a 3/4-inch drive wrench instead. Either way, make sure you get one with a calibrated scale in inch-pounds so that you can accurately tighten your plugs to the recommended specification. And, of course, the price will vary depending on the quality and features of the particular wrench.
A good quality torque wrench can set you back $40 or more, while a cheap one from Harbor Freight may run around $8 – and if you’re patient, you can even find them on sale for under $5. The most significant difference between a nice torque wrench and a cheap one is accuracy, so if your budget permits, I’d recommend going with the more excellent model with better calibration.
How often should you torque your plugs?
If the car has never been driven or was recently taken out of storage, you can tighten them as much as 15 foot-pounds. When the vehicle is first started and the engine is cold (not warmed up), tighten your spark plugs to 12-foot pounds. After warming up, recheck all spark plugs at idle to ensure they’re still at 12-foot pounds, then again with a quick acceleration.
The one place where this isn’t true is if you have a turbocharger or a supercharger that runs off the engine’s accessory belt – in that case, follow manufacturer recommendations for how tight to make those belts. They run from 20-25 ft-lbs on some Hondas up to 65 ft-lbs on some Ford engines.
How accurate does a torque wrench for spark plugs need to be?
On a 2 inch drive, any reading over 3% is considered suitable for most applications. That means your wrench can vary by as much as +/- 9 inches per pound and still be satisfactory.
So don’t just buy any old $10 wrench from Harbor Freight and expect it to work, at that price, I wouldn’t even trust it around bolts or screws, let alone tiny little spark plugs! You’ll want something with accuracy within +/- 4%, which might run you as much as $40 or more depending on the quality and features of the particular wrench. However, if you’re patient, you can find good deals on quality torque wrenches by waiting for sales or looking for refurbished models.
Always consult your vehicle’s service manual for the specific torque specs that apply to your make and model. And remember, using a supplemental wrench can help you achieve an even more consistent level of torque, something that’s especially important when dealing with spark plugs.
- What is torque?
Torque is a measurement of how much force is applied to an object, typically in pounds-feet or Newton-meters.
- Why is a torque wrench necessary for spark plugs?
A torque wrench is necessary for spark plugs because it ensures that the plug is tightened to the manufacturer’s specified torque level. Too little torque can lead to a loose plug and misfiring, while too much torque can cause the plug to crack or break.
- How do I use a torque wrench?
To use a torque wrench, first consult the manufacturer’s instructions to determine the correct tightening sequence and amount of torque for your specific make and model of vehicle. Next, find the correct.