Wow, that’s a really loaded question.
At one point in time I had at least two dozen ST 46 engines that were reworked (Randy Smith, Big Art, Big Jim, and others) and others some were stock from the factory. They all ran great but all had the same problem, after about 5 to 10 gallons of fuel the power would drop off a little and you could tell it was time to change the ring. Thinking it was a fuel problem I switched to all caster fuel, it seemed the normal SIg fuel made the rings last longer mainly because the carbon was washed away from the piston, the all caster fuel had the most carbon on the piston ring groove & piston. I would purchase 6 factory rings at a time and keep the best fittings rings and sell the rest, after sanding the inside of the cylinder lightly to remove the glaze from the inside, sometimes that helped restore the power back to the engine.
Props: The best prop at that time was a 11 X 6 EW Rev Up with a under camber sanded into the back side (,030) of the last 1”. This really helped in the Hourglass & Overhead’s to keep the line tension where i liked it. I tried a bunch of props but in the wind I found that 12 X 5 W Rev Up was slightly better in strong wind.
Line Length: Most of mine were flown on .018 X 64’ lines with lap times around 5.2 to 5.4.
Model Size: The Magnums I was flying all ranged between 52 to 58 ounces with the lightest being the I Beam Magnums around 46 to 51 ounces.
At this point I switched to the ST 60 and that in itself, was another story, with the introduction of the
Smith PA 51 & 60 were the engine of choice out there.
Later,
Mikey