The aluminum head is the lesser part of the equation.
Ford, it their infinite wisdom, engineered a head with too little room to allow the plug threads to be directly above the point of entry into the cylinder (for whatever reason) and instead, opted for a long-tail plug that extends the spark electroded into the combustion chamber, but keeps the threaded portion 1" above. Add to the mix that the clearance between this long plug tail and the bore that contains it, and stir it all together with a two-piece crimped plug, and you have the perfect storm of tight tolerances, carbon fouling, and weak plug construction. Presto!!! Broken plugs and high maintenance costs. The fact that they sold a kabillion of these engines and are not steppping up to cover their comedy of errors makes me wonder how much longer I can remain a loyal customer. I know they've all made junk at some point, but this situation is inexcusable and yet it flies mostly under the radar, as ignorant multitudes just figure that's the way it is in today's "high-tech" world, and they just pay the bill.
HOGWASH!
