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| How to Cut Back Spark Plug Electrode |
| Background Standard spark plug design has the ground electrode entended over the center electrode. This design tends to shroud the flame front from the mixture, reducing burn efficiency. |
| Solution Cut the ground electrode back so that it extends just to the near edge of the center electrode, as shown in Figure A. This can be done with a cut-off wheel on a Dremel or by using a file. Then take a fine file and remove any burs or sharp edges from the cut end. Gap the spark plug per your ignition system capabilities. With my enhanced ignition system a gap of .045" to .048" works quite well. |
| Test Results After running cut-back Split Fire spark plugs for some time at the strip, I installed some unmodified Rapid Fire spark plugs at the same gap setting and subsequent trap speed was down by 1mph. The following weekend, with the old cut-back spark plugs back in trap speeds were up by 1mph, to their former level. This 1mph increase in trap speed is equivalent to a gain of about 10 HP. Though other mods have been made along with the spark plugs, I now get 31mpg on a long trip compared to 29+mpg when the car was bone stock. |
| Reference This hint was first read in TPIS "Insider Hints" and later in Dave Emanuel's book on SBCs. |
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| Figure A - Spark plug with cut-back eletrode. |