It's not unknown to get a slight weap to the rear of the exhaust manifold between the cylinder and the head. This gives off fumes not unlike a petrol leak and can go practically unnoticed because the engine gets so hot it burns most of it off. Hence the smell.
I've had the crankshaft oil seal changed twice now. Oil from this tends not to go back any further than the chassis cross member at the front of the engine.
