Hot Rods Spark plug wires.

Solid core will last until BAD corrosion gets in or the insulation gives up.
Suppression core wires can degrade over time, but most often fail due to heat, the insulation again or rough handling. Some were cheap and not great still in the box.
Just ohm checking isn't great, due to such a small voltage and current flow compared to normal high voltage operation. 'Scoping is best, but when was the last time you saw a 'scope in a regular shop? We are talking about 60 year old tech, modern stuff sets DTCs for misfires. Even plug wires are old tech now for the most part.

Considering most HAMB engines run cooler and have less tight engine confines, a quality set should last for a very long time provided they are not handled roughly. Most have much fewer miles per year than daily drivers. It's not like we are doing a complete plugs, points and condenser tuneup every year.

 

If you do not have access to a scope, the next best thing is a continuity test. That will find an open or really high resistance wire. However, p***ing a continuity test doesn't mean a wire is good. Testing it with 20 -40K volts is the only real test (scope). I've read a lot of threads where a person has an engine running problem and have replaced everything with no success. I suggest they find someone with a scope who knows how to read it. In minutes you can find an ignition problem or verify that the problem isn't ignition.

 

Almost every driveability tech working today has a scope and uses it daily. On a DTC missfire it allows you to narow down the part of the system that is setting the DTC. It doesn't look like the old Sun Scope, it looks more like a tablet. It is used on many of the electronic systems on new vehicles. Many use it in lieu of a voltmeter. A scope catches anomlys that a meter can't. You can still use it to scope the ignition system.

 

Primary or secondary (plug wires)?
I know they have tablet 'scopes, but didn't know they could capture with an included inductive lead rather than the typical wired leads. Looked at this one and sure enough you are right. Secondary inductive! I didn't dive in deeper, do they do the old school full distributor patterns?
https://store.autel.com/products/maxiscope-mp608

BTW, 'scoping alt output was a big help in finding issues too. A bad diode wouldn't always show on a voltmeter.

 

The oscilloscope is absolutely still very useful for diagnosing modern cars, ignition an loads of other systems, even mechanical issues.
The fault codes only lets you know where the car sees something outside the allowed parameters, unfortunately that's a broken computer diagnosing itself, and even if the fault hasn't limited it's ability to do that it's very much limited by the information it has access to and the programming. Just for example, the computer usually interprets a sudden reduction in rpm as a misfire - that makes sense, right? A bad CV joint that is very hard to turn past one position can cause false misfire codes as rpm goes down when p***ing that position, and if you go to the shop that only replaces parts based on codes and guesses you will spend loads of money on ignition coils, fuel injectors, probably a computer or two, before they give up and give you back the car...

On an old points equipped distributor ignition the oscilloscope can often pinpoint what part is bad. Nice when you don't need to swap everything at once, or try one part at a time.

 

Hello,

Your friend is on the right track. If the wires are not cracked or melted by accident or not, they are working just fine. if the cap is cracked or melted, then there is cause for replacement. But, if your motor is running fine, I would not worry about it. Although, i would not want to be out 50 miles away from anyone in the middle of a barren Baja Mexico, surf journey and have the motor stop for some reason.

Changing spark plug wires on our 65 El Camino was never done, even if it had 125k miles when we sold it to a local buyer. I had moved the stock wires to route it nicely, not touching the headers or other hot engine parts. I had a roll of Packard 440 wires sitting in the backyard garage my brother and I built. It was for our Impala and for our 292 SBC supercharged motor. We made custom lengths for both motors and that always prevented the hot header pipes to touch the wires.

When one of my friends asked me to help him change his wires, I was amazed. I thought those were standard car motor items and if nothing is touching the wire covers, then they would last forever without any maintenance. All of our cars had wire like others, but we never changed the complete set. Except for the Impala and the 292 671 supercharged, blower spec motor with new Packard wires.

Jnaki

On the flathead 40 Ford Sedan Delivery, I had to change three wires due to how old they were and they were touching hot metal to slightly melting the cover. Then, later, I questioned the stock wire system we had from our old 283 carburetor powered motor.

My brother wanted all new stuff for the newest build of our old SBC 283 motor. The 283 SBC motor always had a difficult time with routing the wires. But clips and hold down screws did the job.