Well I see a huge problem with trying to do what your pondering.
1: the engine needs to "free rev" to get up to its intended power range and then you "pull the load" This will show max HP
2: then you need to "pull a load through the rpm range" to see what sort of power curve you have.
This is why dyno's are so expensive ,you need a counter force and program to run and adapt this counter force. The formula for calculating HP is pretty easy with a propeller if you can find the correct diameter and pitch , BUT and this is a huge BUT , after a certain rpm things start to get pretty hairy and things can come apart! Those model engine props are not rated to turn much over 25K RPM'S , and most car engines are just coming into it at that speed.
So beware. I have seen blades shed and the out come is catastophic!
(used to build F1 pylon engines)
And as for dyno data, It's fine for an idea as to what your looking for ,but I definately would not base an engine choice solely on this info!
