This video will explain the clutch shoes and spring. This shows a guy taking apart a CXP .18 engine/clutch assembly and the procedures are applicable to most engines and clutches.
The Tornados come with the .18 engine and that's about the limit of how large an engine most people would want to stuff into a 1/10 scale car. 1/10 scale cars used to come with .12 sized engines! Unless you're careful on the gas, you'll spend more time with the wheels spinning than just tracking. I run mine on the road a lot and even with all that traction it still spins all 4 tires and pitches out sideways coming out of turns. Put it this way, I've burned 3 sets of tires right off my rims, about 1 set for each gallon of fuel and I drive the car pretty conservatively because I'd rather run the thing than wait for parts and wrench on it.
Just type "Tonado, Tornado BB or Atomic Warhead" into the search engine at YouTube and you'll get tons of videos of guys running these cars and most of them can barely control them. They just end up doing doughnuts because these cars take some getting used to before you can really use all the power they have.