11-29-2012, 09:27 AM
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Registered User
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Join Date: Mar 2007
Location: DELAWARE
Posts: 1,041
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Quote:
Originally Posted by Air&Road
I have changed plugs in my M103 many times, but I also am getting old enough that my memory is not serving me well.
I remember 10 or 12 years ago Benzmac (Donnie) recommending the Bosch plug and closing the gap a little tighter than the factory spec. I have done that with every plug change since that time and it improved idle quality and general performance. Now, however, I can't remember how tight. I THINK I've set them at .032" but I don't remember for sure.
Even though I'm old, I still have a great memory. Problem is that it's kind of short.  |
I'm also old in my 60's.....your .032" or .80MM gap is just fine 
From NGK:
3. Gapping
Since the gap size has a direct affect on the spark plug's tip temperature and on the voltage necessary to ionize (light) the air/fuel mixture, careful attention is required.
While it is a popular misconception that plugs are pre-gapped from the factory, the fact remains that the gap must be adjusted for the vehicle that the spark plug is intended for.
Those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap settings (to ensure ignitability in these denser air/fuel mixtures).
As a rule, the more power you are making, the smaller the gap you will need.
A spark plug's voltage requirement is directly proportionate to the gap size. The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air/fuel mixture maximizes burn efficiency. It is for this reason that most racers add high power ignition systems. The added power allows them to open the gap yet still provide a strong spark.
With this mind, many think the larger the gap the better. In fact, some aftermarket ignition systems boast that their systems can tolerate gaps that are extreme. Be wary of such claims. In most cases, the largest gap you can run may still be smaller than you think
http://www.ngksparkplugs.com/techinfo/spark_plugs/installation.asp
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