This book is an outcome of successful experimental research on the temperature of the coolant that significant influence on engine performance and emissions. Since coolant temperature can't be varied in air cooled engine. So an attempt has been made to change the heat transfer rate by modifying the geometry of fins. Purpose of changing the fin design may be different according to the need. There can be a need of heat transfer intensification methods to build a lighter model or it can be need of lowering heat transfer rate to decrease the harmful CO and HC emissions. Therefore fins geometry is being changed to bring these effects. Key Features: # Visual Display - The book has quite a number of pictures of the experimental set-up used for an easy understanding of the engine geometric modifications. The impact has been discussed elaborately with the help of numerous graphs with actual readings.