I am building a Velocity and it happens that I purchased a zero time rebuilt 250-hp Lycoming IO-540-C4B5 engine. I have been told by a maintenance shop that the only difference between a C4B5 and a D4B5 is the setting of the fuel servo. The D4B5 is rated at 260 horsepower, and they claim they can adjust the servo to convert the C4B5 into a D4B5.
Source: general aviationCan my engine really be converted with just a simple adjustment?