I JUST SPOKE WITH A RACING TECH FROM AUTOLITE ON THE TORQUE SPEC FOR THE S-197 GT MUSTANG 4.6 LITER ENGINE. HE INFORM ME THAT YOU SHOULD TORQUE THERE HT-1 SPARKPLUGS TO 12 TO 15 FOOT POUNDS NOT TO 25 FOOT POUNDS LIKE PEOPLE ARE SAYING ON THIS FORM SITE. ALSO I CONFIRMED THIS BY TALKING TO MARTIN FROM BRISK SPARKPLUGS OUT OF THERE HOUSTON OFFICE. I THINK THERE IS A PROBLEM WITH CYLINDER PRESSURE THE BLOW BY AROUND THE THREADS AND SEAT OF THE PLUG IF THEY ARE OVER TORQUED. BY THE WAY AUTOLITE MAKES THE MOTORCRAFT OEM PLUGS FOR FORD FOR THIS ENGINE DESIGN.