At FL240, 28", 2500 RPM and 20.5 GPH (rich)  has the engine producing 75% power resulting in a 275 KTAS. If I push the power up to 100% (35", 2,700 RPM and 31 GPH) I'll be zipping along at just over 300 KTAS.  I always keep the CHTs under 400F, the TITs under 1500F and the oil under 195F. The engine in my IV-P is a Lycoming TIO540 with 8.5:1. pistons.

A C150 will do 300 Kts with enough of a tail wind, so what? Boasting about ground speed with tail wind is like telling people how tall you are while standing on a pile of books.

Regards
Brent Regan

<<I noticed that Columbia Aircraft has formed a "300 Knot Club" for those flying the Columbia 400 at 25k feet lucky enough to find a 70 knot tail wind and take a photo of the ground speed on their GPS.>>