Why would you bother with the change of engine as stated above the nitro car engines are alot faster than plane engines, why dont you just get a .21 that will fly...
When you take off the exhaust you lose all the tuning of the engine, i have found from karting that you hill have all top end power and the car will probably not even take off. Plus the noise... OH GOD THE NOISE!!!
Just my two cents
Duuurge