Just finished this 90% size Quikray 500 for a Quikray 400. I'm using a Fox BB .25. I ported the engine and with the stock muffler on 5% with some castor added it turned a 9X6 APC 14,500 rpm, 9X5 MA 15,800 rpm. I plan on flying it soon.

Another engine that is strong in the .25-.30 size is the ST .29. I have two of them and they both turned a MA 9X5 15,600 rpm with no modifications on 5%.

Bill