There's no "explanation".
You just do it, like you do sales tax.

Ok - so everyone should now have all they need to figure out k factor. For the op - if you are going to continue to race this car - you may want to consider going to a 998/999 trans with the factory low gear set and a production high stall converter with lockup. Dime a dozen on converters - lockup when you want it (using the electronic lockup feature), low gear set to get you off the line. This package should get you a couple tenths easy. It will all bolt in - just need to change the prop shaft length.

This is an important aspect, but not always talked about with regard to k factor:


In order for the k factor to be able to predict how a converter will respond to two different combos that have different amounts of peak tq, the peaks would have to be occurring at very similar rpm's.

For example, if one motor had 425ft/lbs peak at 3200 rpm, and another had 525ft/lbs peak at 4800rpm...... Depending on the converter, and what the lower end of the power curve looks like on the 525 combo....... It could actually end up having less stall than the 425 combo.

If the converter was only 3000 stall behind the 425 combo, and the shape of the lower end of the curve for the 525 combo was showing it made less tq at 3000 than the 425 combo...... the converter would have less stall behind it.

So, in order to be able to effectively use the k factor to predict the stall change resulting from a motor change, you need to compare the tq output of the two motors at near stall speed.