I just got done test running my first 1bbl Toro. I did no porting except the exahust. I did nothing to the piston or the bottom of the cylender. I just wanted to see how they did like that. It did well. As well as my 2bbl engines. I got 8100 on an APC 16x8. 7500 on a Pro Zinger 18x6. And 6500 on a Zinger 20x6 (not a Pro). That is very good. For the hell of it I tried a 12x12 APC I had here. It turned it at 9800 ! I thought that was pretty funny. I had to lean it way out on the top end. No load. Not much for thrust but a top speed of 110+ MPH Oh I forgot. These numbers were with a Pitts muffler I make and a 12.7mm carb. Same size carb as a G26.