<... very small plug gap can help the problem. I use .010" to .012" on
both ...>
Wouldn't using hotter plugs help?  Wouldn't that "burn" the lead
deposits off?  How about CD ignition?  doesn't that have a really short
rise time?
There's gotta' be a better way than changing plugs more often than oil
... Jim S.

 

The heat range of spark plugs is just a choice between the coldest that will stay clean enough under most situations, and so hot it will cause engine damage.

 

 A street engine is seldom used for more than a few seconds at full throttle, so the street plug is at the higher end of the heat range, just to function.

 

For continous full throttle operation the street plug would be too hot. This endangers the porceline, and adds extra heat to the charge. The center electrode may overheat and cause preignition.

 

The center electrode is cooled by conducting heat away through the porcelien into the shell

(body) of the plug and off through the rotor housing and coolant. A hot plug has a long path and a cold plug has a short path. Extended tip plugs are hotter, retracted tip plugs are colder.

 

With a high energy ignition system you can use the very coldest plug available and still not foul it. If an alternate path (dirt, carbon or lead) develops around the plug gap, the excess energy still jumps the gap as well as lighting the alternate path and removing the dirt.

 

The advantage of the MSD is that at low RPM, the plug will be hit up to 40 additional times in each cycle. So low tip temperatures at idle are less likely to cause fouling. The MSD is a capaciter discharge system. It applies 350 volts to the coil primary windings, and some coils will fail in short order (probably those with internal resisters to overheat). They provide a list of coils that work just fine with that system.

 

In the past 10 years I have not seen a Mazda race car without a pair of MSD ignition boxes.

 

Lynn E. Hanover