I'll level with you straight away: Anyone that tells you X motor is "equivalent" to Y glow engine is just plain wrong.

The problem between trying to equate glow engines to electric motors is that the chemical reaction that releases the energy does not happen in the electric motor. The electric motor is simply a conduit through which the electrical energy is converted to mechanical energy.

Your best bet at making any equivalency comparisons is to equate the displacement of a glow engine with the number of cells in the battery. That said, if you're making a conversion, you start with sizing the battery, then pick a motor that can handle the elecrical energy from the battery. From there, you work on the gear ratios and propeller sizes to make the plane fly the way it should.

There are lots of resources out there. One online source is http://www.ezonemag.com. Read the FAQ first.

A handy computer program to have is MotoCalc. You enter in the vital statistics of the airplane you want to convert, and it will make power system recommendations. Download a 30-day trial at http://www.motocal.com.