Pinky

I had a spark plug back out on me. Granted I was at the 20ish torque I am hesitant to up it that much more than the 22fp I just set it at. I will be re-checking the plugs(that one in particular) every 1,000 miles till I can be assured that that one isn't backing out at all.

2003AP1

Why is it so much worse on our cars then any other car? Is it the higher rpm limit that causes destruction once the plug comes loose?

s2000maniac

you ask and answer your question at the same time..

slipstream444

Billman is exactly right (this is what he does for a living - this is why he is one of the best sources for information on this site). The breakaway torque is higher for a few reasons. The short and simple is pretty much as you stated - the initial friction that has to be overcome is higher than the torque applied. So backing out the plug (or almost anything that needs torquing - with few exceptions) is important to rebase the torque.

Again - just as Billman stated: 21 ft lbs is the recommended torque to prevent the sparkplug from backing out (every S2000 savvy Honda mech/tech that I have spoken with uses this spec). As a few have noted - the Helms manual states 18 ft lbs. However, the problem (especially with new plugs) is the initial torque falls off slightly in part due to the washer on the plug.

I set mine between 27 and 28.5 NM which is right at or slightly below 21 ft lbs. If you're re-torquing plugs that have been in there for a while, I personally bias toward 19-20 ft lbs. 1-2 ft lbs over the spec'd torque will not hurt anything, especially considering most consumer market torque wrenches have a +/- accuracy range of 3-10% depending on the quality and fidelity of the wrench - which is a function of and partially based on the percentage the target torque is relative to the overall range of the torque wrench.

Someone noted an over-torque situation resulting in a damaged plug:
25 ft lbs won't strip out or damage a spark plug - I would be willing to bet either there was existing damage, the plugs were legitimately over-torqued previously, and/or the torque wrench is well out of calibration or lacking the fidelity for more delicate torque levels.

I personally use an inch-lb wrench (with a range in NM for ease of reference) for things like spark plugs - it provides better feel and the resolution needed for things like spark plugs. You should never use a torque wrench designed with a range that extends in to the triple digits for spark plugs. They can have significant slop at the low end of the range and can be easily off by several foot lbs.

slipstream444

I agree for the most part. People do obsess over spark plugs way too much. However, plugs should be checked periodically. I found two of my plugs had gone slightly out of spec (gap) by 45,000 miles. I replaced my plugs at that time.
The OEM plugs should NOT be re-gapped - you just replace them with a new set of Honda boxed OEM plugs (I'm speaking specifically toward a stock or an N/A motor that is not heavily modified). You can get essentially the same plugs aftermarket - and it might be a little cheaper. However, they may not be specifically gapped within the S2000 OEM range from the factory - and again, you should never re-gap these plugs. Doing so will likely damage the coating on the ground electrode. If your motor is still relatively unmodified it's best to stick with the Honda boxed plugs - but pull them every 30,000-50,000 miles to check the gap.

S>>capades

You're absolutely right about the contrast between static and kinetic forces of friction. In general, the amount of force required to overcome an objects tendency to remain at rest (static friction (Uk) will be greater than the force required to keep an object moving (accelerating) along a surface. (Us)

I think the 2 key points behind adding a few foot-lbs more to the 18-19 ft-lbs recommended by the FSM are 1. The obvious reason to account for possible error in your torque wrench and prevent the headaches associated with a spark plug becoming dislodged from the head, combusted and later uncombusted air-fuel entering the spark plug tube, melting coil pack and potentially damaging the delicate aluminum head. 2. Torque force is compromised by using the deep 5/8 socket and 6in extension required for spark plug install, so adding a few lbs is advisable. I start by hand tightening then torque to 21lbs and have been tracking the s$%t out of my S for 3 years now without issues!

In summary, Just do what Billman says and don't ask any effing questions!! :-)

Cheers

Billman250

For the record, I did a torque test on a stock head and stock plug. Starting at 15 ft-lbs, I increased the torque by 5 ft-lbs each time to see what the threads could handle.

I reached 80 ft-lbs, and the spark plug threaded portion broken off the spark plug. The head suffered no damage at all.

This makes 24 ft-lbs a solid number you can take to the bank.

Sideways

I've been using 22 ft lbs of torque for the last 13 years with no signs of difficulty. Thank you Billman250 for doing this test for us. Good to know information.

amnesia

Sorry to revive such an old thread.

I'm getting ready to check the valves in my 09 DBW with 63,000 km for the first time (just read the warning thread!), but I was wondering what I should do if I remove the plugs for the valve inspection and then decide to re-use them. Should I use anti-seize paste this time (ie will the factory anti-seize coating on the plugs be worn off?) If I do use anti-seize, what torque should I use?

Is it even necessary to remove the plugs to spin the crank shaft to get to TDC in all cylinders? I've read that the compression makes it quite difficult.

Thanks for the help,
Amnesia

Billman250

Do not put anything on the threads. Clean and dry, that’s it.