now after reading all this , why dont people if they are building engines in their garage aim for 1 HP per cubic inch ? With good building and machineing practices, that is obtainable wont cost a fortune and you will have a heap of fun doing the buildup. It wont cost the earth to run, One thing I have noticed reading these threads, to make this high horsepower you will be using more fuel, because to get the high HP numbers you have to get the motor to burn more fuel and air by either high revs and or high displacement. So once you have spent the megabucks building these motors you will probably spend megabucks on your fuel bill because there is no such thing as free horsepower. Also is how long do you figure the engines lifetime is going to be 5 minutes or 5 years, it's your choice.