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Re: Farmall 400 Spark Plug Gap
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Posted by IHank on December 23, 1999 at 19:01:33 from (167.142.18.50):
In Reply to: Farmall 400 Spark Plug Gap posted by John H. on December 23, 1999 at 07:06:23:
John- Battery & coil ignition systems, properly done, have their best output at cranking speed. Spark plug gap numbers "in the twenties" are usually for magneto systems, where the hand cranking speed spark voltage output is lowest. The small gap also makes the plug very "forgiving" of come & go type oil & fuel fouling short outs, but at the same time vulnerable to grounding out by big carbon particles blowing around. A narrow gap will have a longer arc burn time when viewed on an ign scope. That makes it a wash as to physical length of spark vs. spark burn time and gives the tecchies endless argument material. The bottom line is that the small gap is easier to fire, fires more reliably, remains "in spec" firable longer as the gap wears wider, fires better thru fouling, and don't sucker you into the "smog stuff" thinking of the 70's & 80's. It is almost impossible to go wrong with a plug gap between 0.025" and 0.032". See also another post in this IH page about bumping up a number or so on the spark plug heat range, for more good to use info. IHappy IHolidays, IHank!
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