Steven,

If you look at the photographs in your reference, the distance from the
seating taper to the tip of the plug is the same for both types. Thus they
reach exactly to the same depth inside the chamber (I would be really
concerned about sticking in a plug that reaches longer than the original -
for a variety of reasons, including colliding with the piston at TDC). The
difference is that one is fully threaded, while the other is not. The fully
threaded one may be able to engage one or two more threads and help a bit
to prevent stripped threads by those who do not believe in torque
wrenches -- especially on aluminum heads (which luckily, our ancient 302
engines do not have...)


"Steven Hilgendorf" > wrote in message
...
> Another weird thing about the replacement plugs is that the threads are
> longer, which appears as if the plug will seat further into the
> cylinder. Here is a site that notes the differences of the plugs:
>
> http://www.v8sho.com/SHO/SparkPlugChanges.htm