Might be a stupid question, how does the supercharger on my engine work, what RPM should it kick in and the boost it gives should equal just how much more speed? vic

A supercharger is always working, there is no "kick in" but depending on the boost level dialed in when the motor was built it will begin to make boost at a certain throttle position/RPM level. The theory is actually very simple. Energy is created in an engine by burning air and fuel. The more air and fuel mixture that can be efficiently burned, the more power the engine will make. You can do this with more displacement, more RPMS, or in some cases by opening up the passages in or out of the engine. A supercharger produces more power by pressurizing the air going in-thus forcing more air in to be mixed with more fuel-creating more power at the same level of displacement and RPMS. By producing more power(torque) at lower RPMS you can turn a bigger prop for more speed.

Ted thanks makes sense, what will the life of the engine be shortened with supercharger versus stock 502 with no modification. vic

Just bolting a supercharger on a stock engine will shorten it's life considerably. Just like anything else-if you squeeze more power from the engine it will not last as long. If you build an engine for supercharging(good valves, good bottom end, low compression, all heavy duty parts) then it can last as long as a stock engine assuming good care and feeding. But if you take a stock engine, bolt a supercharger on and turn up the boost, you are pulling a pin and just waiting for that grenade to go off.

you haven't told us what you are running, what it "started life as", and what mods have been done to it. Hard to give info other than generalizations. Bring us up to speed and we'll try to give answers more focused on your specifics.