Ernie, if those exposed threads got hot enough to cause pre-ignition they would be gone in a very few seconds, pre-ignition caused by red hot spots whether carbon or metal usually has disastrous results in short order. On the opposite end of things the Fox Miracle plug sticks way down into the combustion chamber, in fact I didn't think a Miracle plug would work in my RCVs but they fit just fine. I have an ABC Fox .74 that was contrary and would quit about half the time during acceleration at about 4,500 rpm, I noticed that the plug was far above the combustion chamber in the glow plug hole. I countersunk the plug so the entire idlebar was down in the combustion chamber, still a safe distance from the piston, that engine never quit again.