I'm guessing your OS 80 has an upturned carb at the rear of the engine and uses two glow plugs. If so my son has one of them and it's a very nice engine indeed. It's a ringed engine so needs about an hour of quite rich running in. They're not quite as powerful as the Enya 80X that we also tried in his model but then again, not many 80's are as powerful as the Enya
. If you do decide to invert that engine as was suggested, then it's a simple matter to remove the two screws holding the carb body to the crankcase and flip it around so the carb faces up. That makes tank height easier to match up with the carb.