Deaconblue
Well-Known LVC Member
Have you ever wondered why the V8 ignition coils fail so often and if there was anything anyone could due to reduce the failure rate or likely hood of them failing?
Well let’s first look into why these ignition coils fail in the first place – beyond of the obvious reasons of improper design or manufacturing as well as oil contamination or water in the spark plug wells, the most likely cause is heat. Now it is really impractical to just remove the covers to reduce the heat because the spark plug wells would soon fill with debris. But there are other ways to reduce the heat, especially the heat generated inside the coils themselves.
As the spark plug ages the gap widens due to normal erosion – even on a double platinum spark plugs. This leads to an increased voltage requirement being need to ionize the atmosphere inside the chamber - to jump the gap and to create the required arch (spark) inside the combustion chamber. That increased voltage requirement demands more current flow (amperage) through the primary winding inside the coil. This increased current flow also produces more internal heat which over time can overload the primary windings, leading to insulation breakdown, shorted out windings and a failed coil.
So if a wider gap requires more voltage to create the spark, which in turn requires more current flow and produces more heat, then conversely a narrower gap would require less voltage, less current flow and lowers the internal temperature of the coil – prolonging the life of primary windings. The stock gap setting on the spark plugs is 1.0-1.1mm (0.039” to 0.043”). Maybe this is just a bit too much for the coils. So what if you were to reduced the gap down to around say 0.9mm or 0.032” to .036”. True it’s not much of a change, but it could have a fairly welcome impact on coil life and not cause any ignition-ability or emissions issues inside the combustion chamber.
Another thing to keep in mind is that a medium wire width (0.4-0.6mm) Iridium center electrode spark plug requires less voltage to create a spark at the same gap and chamber load conditions as does a wide width Platinum center electrode spark plug. Plus these medium wire width Iridium spark plug last just as long as the wide width double Platinum spark plugs. Racers love the very fine wire Iridium spark plug, but they do not last very long in a street engine.
So maybe if you would switch from an Autolite APP3924 to say an Autolite XP3924 or NGK 5464 or Bosch 9603 spark plugs and then carefully (with the correct spark plug re-gapping tool) reduce the gap down to 0.9mm from the normal 1.0-1.1mm range, you just might get these V8 coils to last longer.
I know that’s what I am doing soon.
Well let’s first look into why these ignition coils fail in the first place – beyond of the obvious reasons of improper design or manufacturing as well as oil contamination or water in the spark plug wells, the most likely cause is heat. Now it is really impractical to just remove the covers to reduce the heat because the spark plug wells would soon fill with debris. But there are other ways to reduce the heat, especially the heat generated inside the coils themselves.
As the spark plug ages the gap widens due to normal erosion – even on a double platinum spark plugs. This leads to an increased voltage requirement being need to ionize the atmosphere inside the chamber - to jump the gap and to create the required arch (spark) inside the combustion chamber. That increased voltage requirement demands more current flow (amperage) through the primary winding inside the coil. This increased current flow also produces more internal heat which over time can overload the primary windings, leading to insulation breakdown, shorted out windings and a failed coil.
So if a wider gap requires more voltage to create the spark, which in turn requires more current flow and produces more heat, then conversely a narrower gap would require less voltage, less current flow and lowers the internal temperature of the coil – prolonging the life of primary windings. The stock gap setting on the spark plugs is 1.0-1.1mm (0.039” to 0.043”). Maybe this is just a bit too much for the coils. So what if you were to reduced the gap down to around say 0.9mm or 0.032” to .036”. True it’s not much of a change, but it could have a fairly welcome impact on coil life and not cause any ignition-ability or emissions issues inside the combustion chamber.
Another thing to keep in mind is that a medium wire width (0.4-0.6mm) Iridium center electrode spark plug requires less voltage to create a spark at the same gap and chamber load conditions as does a wide width Platinum center electrode spark plug. Plus these medium wire width Iridium spark plug last just as long as the wide width double Platinum spark plugs. Racers love the very fine wire Iridium spark plug, but they do not last very long in a street engine.
So maybe if you would switch from an Autolite APP3924 to say an Autolite XP3924 or NGK 5464 or Bosch 9603 spark plugs and then carefully (with the correct spark plug re-gapping tool) reduce the gap down to 0.9mm from the normal 1.0-1.1mm range, you just might get these V8 coils to last longer.
I know that’s what I am doing soon.
