300 on a motor to race? Hands down the GRP .21. No other motor can match what it can deliver, including the 400-500 motors. No question it's the best motor on the market right now at any price.
I've got right at 5 gallons on mine now and it is a beast. Still going stong. I've never had a flame out or hicup at any time with it. I tunes easy and holds a tune very good. Not to mention it can break the rear end loose on any vehicle, run with or out run anything on the strait, get 9 mins run time, and still be 205 degrees.
It's the perfect nitro engine.