Typically, advance curves relate to engine power output and possibly the heat loads put into the cooling system and exhaust system due to retarded spark timing from optimum values. Plus, the vacuum advance will also relate to ultimate fuel economy during cruise conditions when the combined vacuum and centrifugal advance will usually be in the range of 45+ degrees BTDC at 2500 rpm. I've not seen any correlation between advance curves and misfire, unless severe detonation took place and cooked or broke the spark plug insulator/electrodes.
In many medium duty gasoline engine trucks in the 2-ton rating range, those engines do not have vacuum advance distributors, but only fully mechanical advance. Their advance curve is typically very similar to the mechanical advance in the normal vacuum advance distributor. Why no vacuum advance? The cargo loads plus aerodynamic loads on their truck body and cargo box would result in marginal increases in economy or power, due to their "under load" situation.
In the 1960s, it was customary to "hot rod" a distributor by putting the advance curve spring kit in the distributor and braze the breaker plate so it would not move as it would if the vacuum advance unit was installed. This, they claimed at the time, resulted in more consistent and reliable timing action. The lighter springs would typically be at full advance by about 2000rpm or later, depending on the particular combination of weights and springs. The old Direct Connection Race Manual mentioned just taking the heavy spring in a Chrysler distributor out all together, but then later they started selling a kit with two light tension springs that accomplished the same thing, plus made sure the timing did retard back to normal for base idle.
The contention that a spark either happens or doesn't happen has merit, but there can also be varying intensities of the spark from firing cycle to firing cycle (and cylinder to cylinder) which can result in some mixtures having a full burn and others with the less intense spark getting a less than full burn. The varying intensities with a point system can be due to the peak on particular lobes of the distributor's breaker cam being worn more than others or machined such that they are not all the same height. This leads to varying dwell times for each respective spark, which relates to coil saturation and ultimately, spark intensity and timing with relationship to TDC.
These firing variations can also relate to manifold air/fuel mixture distribution issues where some cylinders get a stronger mixture than others. See the chapters in the Direct Connection Engine Race Manual on that issue and how to correct the mixture/air flow for more even distribution in the manifold. Leaner mixtures are harder to fire off than richer mixtures, typically, but spark energy and spark plug gap are side issues too.
In an ignition system where there are varying lengths of spark plug wires, it is impossible to get the same spark energy to each spark plug with any type of resistance spark plug wire. Of course, using one of the Monel, spiral wrap magnetic suppression wire sets, the resistance and resultant cylinder-to-cylinder variation will be reduced. Of course, using "wire wire" might be an alternative if resistor spark plugs are used, but with the large number of FM radio receivers in automobiles in modern times (plus in the frequency bands the law enforcement people use), it might be best to use the specified spark plug style and resistor plug wires.
The electronic systems, whether magnetically triggered or optically triggered, will typically have highly accurate spark triggering and timing plus dwell values that are equal for each cylinder. Some of the systems have modules that will vary the dwell with rpm also, automatically. It's this high degree of accuracy that is necessary for the emissions and fuel economy performance of modern vehicles, or at least a major component of those engine management systems.
A further refinement of these systems is the "coil-on-plug" ignition systems. Each cylinder has its own coil and it's either mounted on top of the spark plug or there is a short spark plug wire (all of the same length) for each spark plug. This further results in each cylinder getting the same spark as the other cylinders do to further optimize the engine's performance, economy, emissions, and driveability. In some cases, there are even two spark plugs, operated independently, for each cylinder (remember the old dual distributor top fuel Hemi race motors with two separate distributors and ignition systems?). There might be some creative ways to engineer a wire set for a V-8 such that all of the wire units had the same resistance as the longest plug wire in the set without having a wiring nightmare under the hood.
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