My 1950 Chevrolet 3600 with a 216 had been sitting for some 30 years when I bought it. After bringing it home and beginning work I discovered the block was cracked (check it over carefully especially on the manifold side if you live where it gets cold). After determining I needed a new engine I pulled the old one and began selling parts on Ebay. I too had poured oil in at first and attempted to turn the engine over before discovering the crack. I found all the cylinders to be free but one which was rusted solid. Oil and turning had no effect it was so solid I had to drive it out with a hammer and the top of the piston separated. I guess my advice check carefully and give the oil time to do its work. On the other five you could see it had penetrated and gone down the bore.

1950 Chevrolet 3/4-Ton 3600
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