General Aviation Modifications, Inc. (GAMI) and Tornado Alley Turbo (TAT) have received FAA STC approvals for several new, customized modifications to Continental’s IO-550B (300-hp) engines.
Modifications include Taperfin Barrel Style Cylinders, Needle Bearing Rocker Arms, and an upgraded Liquidair Baffle Kit, according to officials with the Ada, Oklahoma-based company. The new modifications are designed to improve performance and durability in the engine, which is used in many Beechcraft Bonanzas.
“The Taperfin Barrel Style Cylinders have a reduced cross section of the cooling fins on the steel barrel part of the cylinder. That change re-allocates the airflow from the lower steel barrel area to the more critical aluminum cylinder heads, where it’s really needed,” said Tim Roehl, president. “This cylinder design, available from both Continental and Superior Air Parts, has been used on other high-performance engines, but never before on the IO-550B. The upgraded Liquidair Baffle Kit can be configured to accommodate this different cylinder design for overall better control of cylinder head temperatures.”
“The Needle Bearing Rocker Arms have demonstrated significantly reduced wear compared to the standard rocker arm bushings. The wear on conventional rocker arm bushings tends to aggravate valve guide wear in those big-bore Continental engines by side-loading the top of the valve during operation. This has been a long-standing problem resulting in loss of compression over time,” added George Braly, head of engineering for GAMI and TAT.
The Needle Bearing Rocker Arms are approved for use on specific models of IO-470, IO-520, and IO-550 engines, both naturally aspirated and turbonormalized. Availability is targeted for the summer of 2019.
Along with the GAMIjector fuel injectors, these new modifications will be offered in a custom-built GAMISPEC 550 engine, assembled for GAMI by a select group of engine rebuilders according to a detailed specification, said company officials. The new cylinders will receive proprietary treatments to balance flow and to provide improved tolerances on valves resulting in improved performance and durability.
The GAMISPEC 550 will carry a three years parts and labor warranty.
The GAMISPEC 550T engines are available in naturally aspirated and turbonormalized configurations and when installed in many Bonanzas can qualify for substantial gross weight increases, company officials adds.
It’s nice to see mods to improve the weak areas of these engines.
However it’s easier to block some cooling air from the cylinder barrel by increasing the size of the inter-cylinder baffles, a little bit more of sheet aluminum. Shaving down the cylinder fins does reduce the weight a few ounces.!
It seems to me that a roller tip on the rocker arm would be a better way to reduce the side load on the valve stem.!? I’ve not seen any wear in the rocker shaft bushings when I’ve replaced cylinders on my Cont. engine.