Frank,


OS introduced ABN pistons and sleeves in the SF series.

The entire (?) SF ABN series of engines were called ABC, without actually being ABC.

ABN is weaker and less durable than ABC.
ABN sleeves sometimes loose (peel) the nickel coating on them, while ABC sleeves last virtually for ever. OS has supposedly improved its ABN sleeves, by adding a copper flash coat, between the brass and the applied nickel, in the late FX and the new AX version of their .46.

The FS obviously doesn't have it.

The best break-in process is detailed in [link=http://www.rcuniverse.com/forum/Tapered%2DBore_Engine_Break%2Din_%2D_Upgraded/m_1850473/tm.htm]this thread[/link].

You can expect power similar to the new FX model, but this engine will be louder.