Moderator & USAF (Retired)
Join Date: Nov 1999
Location: Tucson AZ
2mm of insulation.
Why, to prevent spark leak and allow a wider gap to the plugs without having it arc through the wire, with higher voltage ignition systems.
Example/case in point, near 18-1 compression, msd 7al3 and pro-power coil, is a 55,000 volt system. Spark was collapsing/blowing out with gaps larger than .030 peak performance was attained with .026" gap. Lessor wire could/would have allowed the spark to arc and not even allow the .026" gap....