RE: Welcome to Club SAITO !
[b]KHodges:
It's a relative thing. The "S" engines still have good mid range, and throttle well. And at the top end, there is more power to be had.
But my old ABC FA-120 engines, the low cam ones, idle nicely at 1700-1800 rpm with a MAS 14x8 three blade prop. The FA-120S, while it will spin more prop, is a bear to get under 2200 rpm at idle. Still idles well, just wont do it as slowly.
The "Middle" production, with the AAC cylinders and the low cams, removed the weight penalty that Saito used to have, if you can find one that might be for you if you have to have the low idle.
ABC and AAC. How to tell them apart. Easy. If you have one in each hand there's about 5-6 ounces more weight with the ABC. Looking at the cam box, the larger fins on the ABC wont let you pull the cam without pulling the cylinder first. The smaller fins on the AAC give enough room to pull the cam out with the cylinder in place.
In any case, if you buy new don't be afraid of the "S" engines - they will do the job very well.
Bill.
PS: Attached picture is two FA-120 cylinders. ABC on the left, AAC on the right. Difference in size hits you right in the eye. Please note the AAC in this case is the early FA-120S with the pipe intake rather than the cast. Otherwise interchangeable. wr.