upgrade the clutch bell and clutch spring. i usually just idle 3 tanks thru the car at the factory settings, the 4th i will start to drive it around no more that 1/2 throttle. make sure your piston it at the bottom of the stroke when you let it cool between tanks.

traxxas spring# 4146x (use the spring not the clutch shoes)
http://www2.towerhobbies.com/cgi-bin...&I=LXSP08&P=ML

hpi clutch bell and pinions:
http://www2.towerhobbies.com/cgi-bin...4&I=LXCLR2&P=K
http://www2.towerhobbies.com/cgi-bin...4&I=LXDHM0&P=K
http://www2.towerhobbies.com/cgi-bin...4&I=LXCLR9&P=K