VAP

I don't require lab accuracy but I'd like to know within +/- 100lbs or so what kind of pressure it takes to force a spark plug out of its threaded bore. The trivia value alone is priceless!

;-)

Lago Blue

<center><img src="http://www.sjmautotechnik.com/trouble_shooting/ecupic/F5DPOR.jpg"></center><p>
...wear goggles &amp; use compressed air to clean the head recesses first;

-remove &amp; read the old ones;

-make sure each new one is the correct P/N (matches the box);

-gap new ones if applicable, using an approved tool in the prescibed manner, such as the little folding Bosch tool;

-ensure the top terminals are screwed on tight;

-carefully anti-seize threads &amp; squish-able washer on new ones w/as little compound as possible, &amp; don't get it on the working end;

-thread in by turning socket extension by hand only, just until the washer touches the head;

-I always try to slightly under-torque them a little, as I don't like to totally flatten the washer (as in above photo). By allowing it to remain slightly "sprung", I hope it will still seal well upon re-use. Also, beware that having them anti-seized means that they will be -tighter- at a given torque than if the threads where dry;

<b>Bosch</b> recommends "when installing spark-plugs to use a torque wrench and the correct torque:

Note:
The tightening torques listed apply to -dry-, non-greased and non-oiled threads.

(for our 12 &amp; 20V motors

M 14 X 1,25 with gasket in an aluminum head: Torque: 19-22 ft./lbs.; (20-30Nm).

If a torque wrench is not available, hand tighten the plug until it is seated in the cylinder head. Spark plugs with gaskets should be tightened an additional 90°."

<b>NGK</b> says 18-21 ft./lbs. in the same above situation.

Mine don't loosen at 15Nm (note: w/anti-seize &amp; my wrench). However (your experience may differ), you may (especially in light of the above consequences) want to monitor them to ensure they don't loosen at this (below the officially recommended) torque.

rggpa2

...Thought I was doing it in a non-standard way, but have been reluctant to not flatten the washer first. Guess I'll have to give the "right" way another go.