Transforming a standard Lamborghini 4.0L to a larger size was a real challenge. In order to increase the stroke from 62mm to 80mm required that the deck of the block be raised by 9mm by the use of custom deck plates. After the block was raised, then many other factors are changed as well (cam chain, head studs, tensioner sprocket, liner length, etc.). Additionally, the cam proﬁles had to be re-designed for low rpm (1,500 to 5,500 rpm range). When the engine was dyno tested, the Weber carbs needed to be completely re-calibrated for the larger displacement and lower rpm running range. All of the modiﬁcations were successful and the engine made good low rpm torque which is essential for a marine application. This engine and the sister counter-rotating engine will be installed in a Riva Aquarama speedboat once owned by Mr. Lamborghini.