One of the things I want to eliminate as a potential cause of my high rpm misfiring is EMI due to unshielded plug wires. I  currently have Blue Max EMI sheilded plug wires and just purchased Magnecor shielded wires. What makes these "shielded"? They have a conductor with a very thin wire wrapped around the insulation of the core wire, and that is covered by another insulating layer, and that is covered with the outer sheath. But,my understanding is that the spiral wrapped wire is supposed to shield the inner wire, and the way I have it configured, with the inner conductor and spiral wrap exposed and crimped in contact with the teminal ends, doesn't the spiral wrapped wire also conduct the spark current and thereby defeat the whole purpose? Isn't the shielding wire supposed to be grounded at one end to the engine and drain off any induced current from the high voltage secondary ignition lead, and be separate and not in contact with the
conductor? And if that is the case, how am  I supposed to configure or fabricate the terminals in such a way as to ground the spiral wrapped shielding wire?

Alternatively, I do have some heavy braided wire that I could slip over each entire secondary lead and ground one end of or the other to provide shielding.

Comments and suggestions invited.

Brian Trubee

Yes the shield should be grounded on one end. It is insulated from
the core. Some plug wires have a core that has some resistance
winch is supposed to minimize radiation.

By all means add the braid and ground on one end.

I think somebody is selling spark plug shields.
http://www.overnightautoparts.com/brand/msd.html
http://www.innerauto.com/NGK_Brand/



Paul Lamar