i just put new wires on my '83 240. after the first time i put them on, i noticed that i could wiggle the boot that goes over the plug. with the previous wire i couldn't do that. upon further inspection i found that the part that comes in contact with the sparkplug in my new wires was twice the diameter that is was in my old wires. the reason for this was the sparkplugs that were currently in the car were the type that have screw-on "nubs" for the ends which come in contact with the sparkplug wires. the "nubs" had been removed and the threaded stud was all that was there. the "nubs" weren't on for the old wires, but were needed to fit into the new wires. with the wrong plugs my car still ran, but not very well. i'd recommend getting new plugs, you should notice your car running better.