You did the same thing that I did, you purchased the wrong engine. No worries though. They make a crank just for this conversion. [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&W=000590686&I=LXGMM8&P=K]Here it is.[/link]

I installed this crank and haven't had any more issues so far, and the engine is installed.

Hope this helps.