I just bought An Axial .28 motor for My Dirt Demon.

With my truck stock i was clocked at 40-48Mph on good days even 50Mph. My gearing is stock 12/52.

How much faster will i go now with my new engine?

I can't figur out my speed on this Calculator ( http://www.radiocontrolzone.com/cars/calculator.asp )

whats the rpm difference between the stock and the new one? although it might be easiest to just clock it once its broken in

The Hot Bodies Has 28,000 RPM

And

Axial Racing 36,000 RPM

Differnce 8,000 RPM

Give or take a few miles per hour, it should go too fast! Jeez man it already goes 48mph? That is plenty fast for a truck! Have fun though.

well... if you can actually hit the top RPM on both engines, and you keep the same gearing...

8000 RPM would give you a 28.57%(rounded) increase in speed.
Assuming you hit 48 at 28000, you theoretically, should hit 61.71 MPH at 36000

thats insane. youll have to clock it and see how close that estimate is