I really have no preference as to whether an engine is ringed or ABC. They both have their advantages and disadvantages.

There are many people on the internet that will argue this point till the cows come home.

The ST 40 retail price has been $49.95 (USD) for at least three years.

The newer ones are very smooth running through-out the throttle range and easy to adjust.

A OS 46AX is very user friendly and easy to adjust. Perhaps the best I've ever experienced?

You cannot put a whole lot of faith in those horsepower figures posted in the ads. They seem to put down whatever they want and it is always at some unrealistic rpm. To run a 8-4 prop to get the ST 40 to run 15,500 rpm . . . . Why the plane wouldn't get off the ground.