912ULS NGK DCPR8E spark plugs / tools

Most any 3/8" and some 1/4" torque wrench will work; no need to get all fancy. Many regular sparkplug sockets won't fit - get a thin wall version, available at most Autozone stores. (I carry one with me in the plane since it's not a normal item in an FBO's toolbox.) When backing the plugs out, it should come smoothly and evenly by hand after the initial torque release. If not, don't force it. Probably there's a carbon or lead buildup on the deeper threads, work it in and gently out against the resistance. This should clear off the grime without it getting trapped in the threads which can open them up if you force it out.

"Most any 3/8" and some 1/4" torque wrench will work............."

I beg to disagree.

The steel plugs are being tightened into an alloy cylinder head, its important that no damage is done (over torquing) and that the plugs are secure (not under torqued).

A reasonably accurate torque wrench is, in my view , a must.

If you don't bother you may as well go to the elbow click" , as you would a mower.

Sean Griffin wrote:

"Most any 3/8" and some 1/4" torque wrench will work............."

I beg to disagree.

The steel plugs are being tightened into an alloy cylinder head, its important that no damage is done (over torquing) and that the plugs are secure (not under torqued).

A reasonably accurate torque wrench is, in my view , a must.

If you don't bother you may as well go to the elbow click" , as you would a mower.

There's some truth to this, but there's also some hyperbole. If the engine used to be spec'ed to 20Nm, and is not spec'ed to 16, then that already hints at a very wide torque spec. Furthermore, the lack of precision given in the torque spec (+- how many Nm?) is another clue that it's not extraordinarily sensitive.

Steel spark plugs have been going into allow heads for decades in the automotive industry, and there seems not to be a problem with people tightening them by feel, much less with a precision torque wrench whose calibration certification is still valid.

I think it's fair to conclude that a reasonably prudent approach will give fine results. I don't think I've ever heard of a spark plug damaging a cylinder through overtightening due to a miscalibrated torque wrench. Even if it is happening on occasion, it's certainly not as big a historical risk as crossthreading.

Hi all

Old thread, have not seen this until the last comments.  There is some confusion to be sure about the value of the torque.  This is mostly because Rotax had to switch from NGK to the Rotax branded plugs.  (made by a different supplier)  The SI release at the time shows the value for the "new" spark plugs, the Rotax branded ones, at a lower value than the NGK.  Given that they stopped supply of the NGK from Rotax all specs after only show the values of the "new" type.  This is with the heat paste on the thread as stated.  

What did change from the original release of the SI was the time to exchange plugs.  The original 2017 release showed the same time values as the NGK.  This changed however in all later releases of the maintenance manual line, MML, it now doubles that from the old SI release.  Always use the latest values is the standard practice.  If however you are still using NGK then use the value from that brand.  

Here is the page that shows the values of the "new" plugs.  Page from: 

SI-912 i-013 / SI-912-027 / SI-914-028

Cheers

I purchased my In/lb torque wrench on line.  Used it building my Gyroplane and performing routine maintenance.