Sorry to bust in like that, but dude: keep it real. I have had the engine for testing purposes installed in my car for about a gallon, it was smoothly broken in and perfectly tuned. I was very impressed with the engine in terms of how it develops its power and how high it would rev in regard of its cheaper price here in Europe, BUT come on - my O.S. Speed does not enter the "12-13 min club" under racing circumstances and nor does the Arrow which is closer to the blue O.S. than to the Speed.
With the pre-installed 9 mm venturi it richens too fast while idling and cools down pretty quick which leads to the need of a few high speed laps to get it back on temperature and therefore power. Another test-driver just found out that this problem can be solved with a 6 mm venturi (O.S. fits).
The needles are pretty loose in the carb and need some additional o-rings to stay put.

Please don't get me wrong: I really do like the engine and for its price it is more than an alternative to GO or Alpha engines (especially regarding the low maintanence break-in process in comparison). I liked the feel it had to it while driving a lot more than with the Alpha engines and from what I heard it was even better with the 6 mm venturi. But keep in mind: It is no O.S. Speed, it will never be one. There are the differences that manifest in pricing in the end and that's absolutely okay. If I was on a budget and looking for a good solid engine, the Arrow would be my first choice as of now. I dont know how it is priced in the States and the rest of the world, but if it was cheaper, I would even prefer it to the blue O.S., because they dont seem to differ too much, so pricing would decide.