"440 - 25% = 330 doesn't it"

I'm still looking for the math.

440 x .75 = 330 yes
though not the same as
440 divided by 1.25 which is 352

326 x 1.25 = 407.5
407.5 divided by 1.25 = 326

18% calculator.
http://www.fordmuscle.com/calculators/horsepower.shtml
4000lbs, 12.91 ET
326 RWHP x 1.18 = 385 FWHP
Same as 385 divided by 1.18 = 326

Not the same as
385 - 18% (385x.18 is 69.3) = 315.7

Yes the percentages, 18% vs 25%, are different but the online HP calculator does the math my way.