What problems are you getting, Adam? I'm guessing the engine stops and you have to wait half an hour before it will start again?
The engine has a massive fan built into the flywheel - much bigger and more powerful than any blower you will put in. If that doesn't cool it, there's a significant problem somewhere. I haven't come across an effective blower set up yet
If you give Sue a ring on 01926 356200, she will help you identify the engine (she does a lot of that) and can give you some idea of what might be going on
Richard