340 Blocks

Coyote Jack said

I'm not sure how true it is, but the theory is that if you look at the numbers on the drivers side of the block, they might end with "340-6" or something like that, the lower the last number the better the block should be. ie: a 340-1 would be better than a 340-6. The last number is supposed to represent how many times the casting mold was used.

Jack

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That is true to a point. The 340-1 (sort of like a V1.1) might be inferior to the 340-8 (V1.8) because the casting revision "8" (not number of times it was used) may include slight changes that were needed for manufacturing, eg. a thicker casting rib or a bolt boss or a core shift tweaking, etc. Although most blocks are identical in almost every way, the 400CID Mopar for example had one block that had a noticeably thicker web on the #3 bearing. Check out 440source.com for their theory on casting core numbering. I had a "340-6" block and was doing backflips until I realized it was just the 6th core revision, not a 340 six pack T/A block......