Regards to superten require a fan for 4stroke. The 4stroke engine was originally designed for airplane. As you see all airplane engine doesn't require huge fins or heatsink head to do the cooling due to the propeller is driving air flow over the engine. OS modified the .26 or .40 4stroke to fit on a car without altering the external casting. Secondly, the 4 stroke doesn't have huge heatsink head like our 2stroke due to the over head valves. It's main cooling are from the small fins around the cylinder wall.

The main advantage of 4 stroke engine is fuel efficency and huge torque produce on low rpm. Hence it can geared to very low gear ratio to make up lack of RPM comparing to 2stroke engine. A properly geared car for 4 stroke engine will be just as fast as properly geard car for 2 stroke entry level, 1HP rated, engine. But for each tank a 4 stroke might last 2x than 2 stroke engine so 4 Stroke engine is good for multiple hours endurance races.