Originally Posted by
thefastfred
Big Blocks on glow fuel for a B25 - 91”
FA- are small blocks. More power, less weight, more fragile…. Am i corect on this
All Saito 4 strokes that burn glow fuel are designated FA. It stands for "
Four stroke" "
Alcohol". That includes small, medium and big block Saitos.
All Saitos that burn gasoline are designated FG. Which stands for "
Four stroke" "
Gasoline".
Originally Posted by
thefastfred
Big blocks - pre FA
more robust gears and bearings. Less power…. But by how much?
See answer above. The power to weight ratios are very similar between all single cylinder FA engines. Choose your engine displacement based on required power. Big block Saitos do have a more durable valvetrain than the smaller Saitos, namely the tappets.
Originally Posted by
thefastfred
project calls for a pair of 20-26 cc amd neeeds a 3-blade prop for scale. So a set of 125 big blocks, one counter rotation should do the trick. 150 will fit but there is a point of over power.
( Weight n vibration & fuel consumption ).
As mentioned on the other thread on RCG, counter rotation is not required for our model twin engine aircraft or full scale twin engine aircraft. Many twin engine aircraft do not use counter rotating engines.
The FA-125 is not a big block Saito, the FA-120, FA-150 & FA-180 are big blocks as well as the FG-30. The FG-36 is the FA-220 counterpart, a different crankcase design from the other big blocks.
Keep in mind That when a model manufacturer specifies a 2 stroke gasser 20cc-26cc engine an equivalent 4 stroke glow engine will need to be approx 1.2 times larger displacement to produce the same power. An equivalent 4 stroke gasser will need to be approx 1.4 times larger displacement.
Originally Posted by
thefastfred
Is my head screws on right?
Only you can say.