I put a new .63 in a Great Planes Corsair that I bought almost ready to cover in March. I only had to adjust the high end needle and nothing else. It is a real powerhouse. Like a previous poster, I am always having to answer the question "what size engine is that". Mine has been flawless since it first fired up. I am using an APC 12X7 prop. I would estimate top speed to be 110 or so. In fact, when I pull the throttle down to half, the decrease in speed is hardly noticeable. Unlimited vertical performance from the instant the plane leaves the ground. It also forces me to use that right rudder, especially at takeoff and when doing touch and go's. Worth every cent of it's price.