This is sort of a general question, but also has specific relevance.<br /><br />I've finally got my '64 40HP BIG twin running well after many sessions of tinkering. The one thing I know I "should have", but alas, did not do, was replace the spark plug wires when I had the flywheel off.<br /><br />Again, not knowing the previous history of the motor, who's to say just how old those high tension wires are...I did a visual inspection to see that modern coils in sound condition were in place, set the point gaps, rebuilt the carb...and now things FINALLY run happily...so in a sense, I'm pleased w/ the way my motor works, and figure it makes some sense at this point to stop digging into things and just enjoy it.<br /><br />So my question is not really should I have done so, other than for sound peace of mind to know that w/ a new set it would just be one less thing to fail unexpectedly and also help as a test matter in eliminating unforseen future problems.<br /><br />But, WHY...why ever bother to replace spark plug wires in the first place, if there isn't something visually radically apparent that's wrong (like cracked insulation or broken up boots, etc.)<br /><br />What actually is going on inside wires...would new ones do anything markedly better to improve performance or spark, and if so, why?<br /><br />Spark plugs...well, those I can see...you use them, they fire, the gap changes...but even then, you can regap spark plugs, reset points, and rely on coils working fine for many years (and more importantly, for millions of repeat firing cycles)...electrically speaking, how do any of the components break down or wear out (I've got 30 year old coils in cars still generating sparks properly).<br /><br />So, if they're doing the job now...what's to be gained by new wires.<br /><br />Admittedly, in my daily driven car, maybe once in a very long while, if it's behaving nicely and I have some extra cash to throw at it, I'll put new wires on it...but it's rare, and it's mostly for a sense of feeling good like you're helping out an old beast by doing something you hope to make a difference, but does it really or is it an unwarrented expense?<br /><br />Do the internals of solid stranded wire break down...I know plenty of cases, even in my own experience, bringing back an antique car from the dead, and you can get them to start and run fine w/ their old wires so long as mice haven't gotten to them.<br /><br />Now, since I finally have the motor back at home to work on...and if I could find someone that had wires in stock NOW, I wouldn't hesitate to replace them...BUT, since one way or the other, I have to order and wait for them, it'd be great to know exactly how and why to justify the minor expense and associated labor, other than for the reason that "you just plain should replace old stuff like this" when you tinker w/ things of unknown maintenance history.<br /><br />I appreciate anyone's reasoning (aside from the vagaries of answers already provided).
