Someone I knew back then from work collected aluminum scrap and would take it over to a recycling plant and sell it. One pickup truck load he had had 3 Vega aluminum blocks in it. The scrapper told him to take those blocks back and not mix them up with his aluminum scrap. He told him that the silicone in the aluminum those blocks were cast from would contaminate and ruin the whole batch if they were melted down together. Must have been some real junk metal. If the Vega would have had a cast iron block with a conventional deck and pistons in it, it would have worked. The design was a good one, the overhead cam head was simple and rather clever, but the block was the whole weak point in that motor. Steel sleeves and non tin plated pistons helped, but the freestanding cylinders still moved around too much.