K&B 7.5 DF
windwalker,
Hopefully attached is a picture of a modded Scat Cat with Modded K&B 7.5. Haven't flown it for 20 years but it was close to 150MPH when last flown, I used a Macs bolt on "Fuse Top Header" and a Macs 7.5 Muffled Tuned Pipe. Iused the largest Rev Up Series 400 Pylon Prop available, I believe it was a 8.75X9. It would turn 19500 RPM on the ground and about 21K in the air. The Pipe and header are still listed on Macs Website