I have a 3963512 block that is standard bore. three main bearings are spun pretty bad. The cam bearing opening is chewed up pretty good also. I took it to a machine shop and the guy told me it would cost more to fix it than it was worth. I have had others "tell me" that it is an easy fix. Anybody have any experience they can share with me? Is this thing worth saving or should I turn it into a paper weight?

id say its worth keeping, or just sell it for a few 100. big blocks will always worth something as long as they dont have a rod through the block

Hey
I have seen 512 blocks go for $1500-2500.Don't know if anybody really paid that much for one.It seams that the 512 is the one that the restorers are looking for,1970 L-S6 block you have if the date is correct.Take it to another shop and get another opinion.
-Kid

The front of the block behind top cam gear is easy fix with a bearing about $50 or so. The mains would have to be line bored which would be a couple hundred. Is the block a 2 or 4 bolt and what is the casting date?????

it's a 2 bolt main....cast date june of 1970. (i think, its june ,july, aug. somewhere in that area)

The block is the least valuable of the #512 blocks being for a 1971 car and a 2bolt. For someone looking for a block to build it wouldnt really be worth much in the shape its in, but if U could find someone with a 71 454 chevelle or better yet a vette. It would still be worth a couple hundred. Put it on ebay and see what it brings........ or list it in the classifeid section on this site.