[Rick Parker]

The manufacturer of the head has certainly done enough 3D Modeling and engineered the casting to utilize a particular design and style of plug and therefore reccomends a particular "Family" of plugs with some degree of confidence. The Final selection is left to you. The projected nose plug puts the point of ignition further into the combustion chamber for better combustion. You can certainly use a regular gap (non projected) but will probably sacrifice some power. As far as heat range, their recomendation will be on the conservative side to keep you out of preignition, to avoid internal damage. Your particular combination, jetting, compression ratio, cam and other factors will dictate the final heat range.

Rick