Midwest AT-6
I'm also starting to build a Midwest AT-6 with Robart retracts. I researched the newgroups to see what people were using for power. Some of the engines being used are the OS 1.08 (2C), Webra 1.20 (2C), OS 1.20 (4C), Zenoah G23 & G38 (gas). I actually purchased an OS 1.60 FX and a J'TEC muffler that fit completely in the cowl. Later on I changed my mind because I figured that the OS 1.60 FX would be too much engine and the prop ground clearance would be mininmal. After researchimg suitable gas engines, I bought an RCS 140 (22 cc) gas engine. Although about the same displacement as a G23, it is reported to generate more power turning a 16 x 8 at 9,000 rpm. I'm targeting a finished weight of 14 lbs or less. I came across one newgroup posting about a MW AT-6 with a RCS 140 flying at a weight of 15 lbs and reported not to be at a loss for power.