I have a 86 XJS. I need to replace the battery cables. Can anyone tell me what route it takes?

 

Underneath the car in the transmission tunnel.

May I inquire as to why you are replacing the battery cable?

 

General maintenance. I'm changing battery, battery switch, hi torque starter and thought I'd do the cables at the same time. The old one is hart as rock and the insulation will probably fail soon.

 

Current draw from the starter motor could be as high as 300 - 400 amps, if you use too small a cable you will have either starting issues or the cable will get hot and melt the insulation.

I would recommend at least 600 amp cable.

 

That will be no small task if you mean the long trans tunnel cable. Almost a transmission out job so l would make sure it actually needs replacing.
It is a pretty stiff cable so don't confuse that with ageing insulation.