Back a few years ago, the FTC decided that horsepower was an arbitrary number, and could vary depending on the equipment, the usage of the machine, altitude, quality of gas, etc, etc. (whatever they wanted to blame). So manufacturers have to label engines differently. Honda uses the cc displacement for their model number (more room for the PC crowd to bitch, a GX390 is only 389 cc), and Briggs uses gross torque output for their model number. I believe this rule only applies to smaller (under 16 hp) displacement engines.