Actually, Plymouth and Dodge sponsored NHRA Pro Stock race teams like Dick Landy sox & martin and many other great teams and drivers 1970 these teams were running 16 plug Hemi's dual distributors in late 70's and 71 until Nhra changed the weight rule and so on, so they were the huge part of the pioneering and developing the 16 plug Hemi's of today.
The second plug design operation on our 4th gen V8's allows for elimination of an EGR valve system and the use of VVT all of which provides some marginal benefit to emissions and performance and additional service charges for dealers. Most every other engine mfg has managed to accomplish similar modern day performance and emission levels without resorting to 2 plugs per cylinder. I've been using a wire brush tool on the end of a drill bit and re-gapping w/out issue.
That's a bonus not having that EGR crap. But my window sticker gives me a smog rating of 1, 0 is the worst.
The coils get one cable, and each coil fires two spark plugs, and is mounted right on top of the cylinder.
Not to be confused with the Hemi not being superior to the other valve layouts, and the twin spark plugs not being a far bettter way to ignite the intake charge. In fact, Porsche used the Hemi twin-plug cylinder head layout for their racing cars and possibly still does to take advantage of racing rules that provide less weight penalty for two-valve motor cars. Curious why they don't use the side-by-side single-plug layout if it is SO on par with the twin-plug Hemi? It's because the twin-plug Hemi layout is vastly superior, in spite of the marketing hype of the Other North American Brands.
