Classic/Antique Car Repair: running rough, coil wire, compression test

Question
my 57 mercury started running rough i checked the plug wires and noticed the coil wire arching out . Should i replace all wires or start with coil wire. Its been a while since i change plugs and wires.what else could it be it seems like its getting enough gas.It seems like its missing

Answer
If you are seeing a spark arcing anywhere, you should replace the wire and whatever the spark was arcing to, because the arcing will leave a carbon track which will cause the car to miss under load.  If the arcing was down the coil side, replace the coil, or if it was at the distributor cap, replace the cap and rotor.   Change the spark plugs and wires too, if it's been more than 5 years since you did it, or more than 20,000 miles, whichever comes first.

This may or may not have anything to do with your rough running - but do that first, and then see how it runs.

Get back to me if it still runs rough after you do that - I'll probably recommend a compression test as the next step is if it still isn't running right.

Dick