Buy some of the 1200* heat shield. It comes in a package, I got mine at NAPA. Wrap the line with it, you can cut it to fit.
Second option, NAPA also sells a high heat repair type tubing, it's a little pricey but it works well (some sort of silicon). My starter lead was very close to my header so I put a piece of that stuff over the cable and the heat has not bothered it one bit. You can't burn that stuff with oxy/acetalyne torches, I tried. Personally I would use this. Slice it length wise and put it over the line and secure it.