Distributor car, plug wires, when to replace?

i change every 30.000 but they can still look good on outside and weak in the middle..another way look at plug wires is look at them when dark outside see if you see any sparking going on..good luck....

When I am wondering, I start the engine at night in the dark and take a spray mist bottle of water and spray the wires and cap with it. If I get a fireworks display, I replace them....

Mike

or you should spray gas on um then you'll see if they need replaced talking about wires..and not good idea on spraying the cap as it could crack..

NO. Most of the time you will not be able to tell by looking. Just replace them at the recomended interval and you will not have any problems. I would also recomend using factory tune up parts as they last the longest. Most aftermarket tune up parts are junk.