Well your definately overheating if you are over 270 according to Traxxas. I have historically ran all my cars in the range of 230 - 250. I usually run in the 230 range. Keep in mind that you should always measure temp at the glow plug and with the body on after you done a few passes. Hope this helps.
Keep in mind that measuring heat is only a TOOL in the tuning process. Every engine will run best at a different temperature. The same engine will also best a different temps depending on the conditions, some listed above.
Tuning by temp alone isn't a good idea however temps will let you know if your close.