Help - Spark Plug Resistance?

[tom1394racing]

I am finishing up the build of the engine for my '70E project and am confused about what type of spark plugs I should be using. I had my CDI box refurbish by Kurt at Partsklassic using his "digital" technology. I checked all my spark plug wires and found about 1,400 ohms from the cap to the plug connector. All of that resistance is in the Beru plug connector. The attached note that came with the box states that I need to use a late style spark plug with a 5,000 ohm resistor to give me a total of 6,000 ohms in the system. In all my previous experience with CDI and MSD fired engines I have used standard zero resistance plugs. So this note has me confused. What am I missing?

[edmayo]

Not missing anything Tom, just use the resistor plugs. Think of it this way, if you were to hold the spark plug wire a 1/16" from ground the coil would generate only enough voltage to jump that gap, if you increase the gap the coil will produce more voltage to jump the gap, eventually you could increase the air gap beyond the coil's ability to generate sufficient voltage to jump the gap. The designed resistance of the plug connector and now the resistor spark plug is to make that coil generate more voltage and thus have a higher voltage at the plug electrode to ignite the mixture. This may be an overly simplistic analogy but you get the picture, resistance isn't necessarily bad. I once put non-resistor plug ends on a M.B. V-8, thought I was doing the right thing,,,WRONG !! not enough voltage at the plug tip for proper ignition.

[tom1394racing]

Thank you Ed. Being a mechanical engineer, I tend to think of electrical things like fluid mechanics. Your explanation makes perfect sense.