Last year when I was using my rototiller for whatever reason a hole popped in the side of the crankcase area. Seems like it was presure build-up that caused it. Engine still works but along with the hot air oil gushes out og the hole. What I don't understand is what would have caused this to happen in the 1st place? I can replair the hole but I'm afraid same thing will happen again. Unless I can get to the bottom of the cause.

It won't work with a hole, and that usually happens when the engine throws a rod.

So the engine is still running fine? I'd tear it down and find out where it came from, the internal crankcase pressure wouldn't do that. Briggs engines have pretty strong engine castings.