The Chrysler lean burn ignition from the 70s was just a MSD in a Chrysler box. I use two MSD 6ALs with built in rev limiter. With the plugs gapped at.012" we have no problems, too rich or too lean makes no difference.

BTW Klause also mentioned that a longer gap has a higher probability of finding a fuel molecule to ignite. He recommended a .016 gap for an aircraft piston engine.

Tracy Crook wrote:
I'm confused.  In my experience, even .016 is an anemic gap.  Check out the gap on a stock Mazda rotary plug (not adjustable).  It's something like .040" - .050".

The problem is that while the engine is at 9,300 RPMs and you are waiting for 9,500 RPMs to shift to the next gear, the engine will show a light missfire. Investigation shows a worn electrode and, or, dirty plug. We run way over rich idle mix to lubricate the apex seals and cool the rotors during closed throttle operation. (the oil is in the fuel). This leads to short plug life. The plugs are very cold and build up crud quickly. It is not mechanicaly possible to gap the NGK racing plugs to much more than .020" but you can tap the ground electrode down into the shell and get it smaller. If you won't spend much time above 9,000, then .016" would be small enough. At 6,000 to 6,500 RPMs it would seem the street plugs would work fine with almost any ignition system.
Lynn E Hanover

 
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