I recently ran across this great discussion because in searching, I found that I have the same type of block that I thought I was going to use for a build but now will not use because of cracks on the deck water jacket. I noticed that there was a lot of talk about the bottom end of this block but really nothing about the top deck. I thought it would worthwhile to mention that the deck on the 1980 "R" 318 block is significantly different then the 1969 318 block I took out of the car. The 1980 "R" 318 block has many more water jacket openings. My "R" block has 6 cracks between the head bold threads and the water jacket (look between the pencil markings in the picture). I assume someone at one time over torqued the head bold significant enough to crack the block deck. Or it had water in it and if froze. Beware of these "R" blocks.
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