I bought a 58 235 engine. I took it apart today, it has aluminum pistons in it. Did they come like that? I bought a 55 235 before and it also had aluminum pistons. The 58 turns over by hand easily, I adjusted the rockers and cleaned the oil pump screen. I found some sludge in the oil pan, and it sticks to the magnet. The engine did not have an oil filter. What would the sludge be from? The guy I bought it from had got it with a truck he bought. So he didnt know anything about it. Im trying not to stick alot of money into it.