The 18 TZ is a good engine whith lots of power and torque. I use it for competition in outlaw class with my MTX4R Kawahara 220mm kit. My tips whould be use it whith no more than 20% of nitro whith 10% or more of oil, OS P6 turbo glow plug, adjust the clutch and 2 speed to engage a litle bit earlier to avoid drive train problems and use it whith lower gearing combination to reach higher top speed. I think this engine is capable of make 80+ mph, however, there`s a lot of factors involve like the 1/10 kit you`re using, engine tuning, tire diameter, glow plug, fuel, etc. Hope this help.