RiverRat2
Serio Tree Freak
The 066 BB (prototype) stock is behind a stock 066 jug, though it does have great low end.
Once modified they are pretty close in cut times, however it is not easy to take the 066bb to the same level of modification as an older 066 Stihl jug (not the new 660 as it is different). Squish on the bb comes out pretty close ~.020 to .025 with the gasket in.
The gains from stock to modifed that can be made are greater with the BB mostly because the BB start out a little lower. The main performance issue I noted with the BB was very short transfer duration.
The 066 BB does turn lower RPM than the Stihl jug both stock and modded with simmilar port numbers. But does make up for that with some torque.
There may be changes to the BB before it becomes final production, so who knows?
That is what I am hearing that is why it is being delayed in being made available to the general public just yet was supposed to be in late Jan now late Feb is what I was told due to changes.............