thats the range anywhere in between there is just fine. I'd do .44 and call it a day.

 

yeah i guess somewhere in the middle will work just fine. thanks. I still would like to know what the difference is.

 

That is correct it just a range. Anywhere in that range will work. If you buy the new irdium Motorcraft plugs they will come pre gapped and you are not supposed to try and reset them apparently the irdium tip is a bit fragile.

 

i think industry standard is around .44

 

Well lets think about this spark plug gap question a little more.

The gap to some extent has an effect on ignition timing.

For example, the wider the gap, the longer it takes for the voltage to build & jump the gap, so it in effect is like retarding the timing some.

The "heat" & "size" of the spark is also affected & that can effect the sparks initial ignition point, "plasma kernel" & thus the quality or the flame front, that spreads accross the combustion chamber & that will affect how well the engine starts on a cold day & the engines power output, economy & polution levels, during a drive cycle.

Also a spark gap always gets wider with use!!!! As it gets wider that plasma kernel gets cooler, the spark gets weaker & if weak enough, can blow out & we'll get a misfire, or poor combustion & thus lower power out, worse mpg, more work load for the cat converter & more polution, a nasty cycle, for so simple a thing!!!!

SO, I always gap my plugs to the minimum side of spec.

This way the spark gap will stay in spec longer & with 100K service life, you know a plug gapped to the wide side of spec to begin with, won't be any where near in spec by then!!!!

For example, when new, I pulled & set my 99 4.0L plugs to min spec & by 50K miles they were already .008" over max spec!!!!

So those of you with 50K or more, need to pull & regap those danged plugs!!!!

You may find setting to the min gap, will help some on really cold starts & when your battery is weak.

Just some more thoughts for pondering.

 

that's more what i wanted to learn pawpaw. thank you very much sir. details,details...