Yea i just got a 300ex with the motor out of it because of the same problem. Except mine had a half inch hole 2 inches long. I put a piece of alluminum over it and sealed it up with some stuff called Lab Metal. Hopefully it can withstand the conditions, specially since it was like $25 for it with some solvent/thinner. Now that I'm getting it back together I'm finding all the things missing. Very disapointing hearing about this "common Problem" though, happens to me again it will probably ruin more than just my case.

 

it sucks not having a garage i have to work in the back yard so i can only work on warm days and its been cold for the past two days. it may go on intill i go back to school on monday then i can only work for a max of two hours before i have to do homework.

 

got the epoxy on the case and the engine is going back in tomar