Belgium, I am SO sorry that this had to happen to you. As a professional mechanic, I am disappointed and ashamed for my profession when I see work of such a low quality. It would not surprise me if the machine shop called you back and said that the crank was scrap, due to the poor ballance job that was previously performed. I would look into using the higher compression pistons, as the low compression 440 was a pig. Best of luck to you, and I hope that your further adventures with this car are much more positive.