The New Engine

The B35 Bonanza came from the Beechcraft factory in 1950 with a 196-hp engine with a pressure carburetor and an electric propeller. Over the years, the engine in N666JS was upgraded, most recently to a Teledyne Continental Motors (TCM) E225-8 producing 225 horsepower. Additionally, the electric prop was replaced with a more modern hydraulic prop. To control this propeller, a Rube Goldberg sort of device known as a T-Drive was developed. The T-drive utilized engine oil to adjust the pitch of the propeller. Although the T-Drive works well most of the time, it can be problematic and is prone to leak oil.

Faced with the prospect of a complete tear-down of the existing engine in order to return it to service, we (my partners and I) elected to explore other options for a powerplant. After extensive research, we settled on the TCM IO-470N Series. This engine is fuel injected and develops 260 horsepower at 2,650 RPM, providing significantly improved climb performance. At the same time, we elected to go with a new McCully 3-blade propeller. This also improves the climb at the expense of a slight speed reduction at cruise compared to a 2-blade propeller.

Although it would seem that the increase in horsepower would result in an increase in cruise speeds, adding power is a very inefficient way to add speed. Since the drag goes up with the square of the speed increase, adding the 64 horsepower could be expected to add perhaps 8 knots at cruise. The real benefit comes in using the extra horsepower at low speeds to improve short field performance, reduce takeoff roll and increase climb performance.