I had partially rebuilt the engine in my 78 Honda Accord, while in HS and had been turing the crank with a large socket wrench through the fender of the car. Honda left a hole there for the socket and extension to reach the big bolt. Once everything looked OK and in time, I got in the car to start it for the first time. I heard this really loud sound and I'm sure my eyes looked as big as dinner plates looking at my dad through the windshield. What the heck was that! I was sure I did something wrong putting it back together. Nope. I left the socket wrench attached to the motor through the fender hole. The direction of the motor was reverse of the tighten direction of the wrench and it was free wheeling at engine speed.