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Im looking for opinions on this block I wasnt able to link this from ebay but it is Item 123557081350. Ive seen a lot of early 721 blocks and I have some with 63 cast dates . This one is intriguing to me because of the very early casting date and the fact that it has the 721 cast upside down on the sides of the block. I know the 721s were used for 283 and 327 applications, but Ive never seen any of the early ones (pre-63) with the upside 721 because to my knowledge the pre-63 casting became 283s for 64 production cars and the upside down 721 blocks were bored up to 4.00 " for 327 applications. This one has the upside down 721 and a casting date of Nov. 17 1961. He tells me the block started life as a 283 and is at .060 over . Before this, the earliest 721 block Id ever heard of had a 1962 casting date.
 

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Good question. I had never heard about the 'upside down' 721 casting, nor have I ever heard of anything but a '63 casting date to the first Nova 283 engines. One with a '62 casting date I'd like to see, and I might be skeptical.

At different times these blocks have been described as 'thick wall' or 'high nickel content' 283 blocks that might be able to be bored to 4". On suggestion of someone that has successfully done it, it was recommended that the block be sonically checked for thickness and a true casting so that there's enough cylinder wall to accommodate the machining.

Any definitive info either way would be good to know....
 

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Good question. I had never heard about the 'upside down' 721 casting, nor have I ever heard of anything but a '63 casting date to the first Nova 283 engines. One with a '62 casting date I'd like to see, and I might be skeptical.

At different times these blocks have been described as 'thick wall' or 'high nickel content' 283 blocks that might be able to be bored to 4". On suggestion of someone that has successfully done it, it was recommended that the block be sonically checked for thickness and a true casting so that there's enough cylinder wall to accommodate the machining.

Any definitive info either way would be good to know....
To my knowledge, the blocks with the upside down 721 were bored to 4 inch for 327 and the upside down 721 was to inform the assembler on the line to install 327 parts. other than that I think they are same casting. The 327 versions being used in production cars in 1965 and used as some early L-79s until the 362 blocks came in. Thats one of the things thats very strange about this block on ebay. It started life as a 283 but has the upside down 721 denoting it as a 327. That coupled with the 1961 cast date makes this a weird one.
 

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https://www.ebay.com/itm/Rare-721-1...k-chevrolet-62-1963-63-64-65-L79/123557081350

I have followed these blocks for quite a while now, and have 7 original 1965, 327, 3790721 blocks with the upside down 721.
I have now seen 2 that were destined for early Novas for dealer installation which were cast in 61 or 62.
I'll bet that one was one of the 1st cast for dealer installation, and also believe it started life with a 4.00" bore.
It's too bad that the block stamp is long gone!
 

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Cool. I didn't know the details. Very weird, or is it? Pretty widely known by now that Bill Thomas (and apparently, others) installed small blocks in '62 and '63 Chevy IIs, both 283s and 327's, and they were recessed oil filter boss blocks. The ebay block has to be one of the very rare and early blocks, and I'd love to know the history. Were any of these stamped after dealer or private installations? And even if they are 4" now, how can someone be sure they didn't start life as 283 engines? Adds a lot of credence to dealer installs of V-8s in '62 and '63 cars, but I'd think they would likely have gone to Bill Thomas type shops that could adapt them to weaker rear ends and transmissions of the first two year Chevy II's. This block is pretty special and pretty rare, it seems.

Find some cars for those '65 blocks!
 

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Cool. I didn't know the details. Very weird, or is it? Pretty widely known by now that Bill Thomas (and apparently, others) installed small blocks in '62 and '63 Chevy IIs, both 283s and 327's, and they were recessed oil filter boss blocks. The ebay block has to be one of the very rare and early blocks, and I'd love to know the history. Were any of these stamped after dealer or private installations? And even if they are 4" now, how can someone be sure they didn't start life as 283 engines? Adds a lot of credence to dealer installs of V-8s in '62 and '63 cars, but I'd think they would likely have gone to Bill Thomas type shops that could adapt them to weaker rear ends and transmissions of the first two year Chevy II's. This block is pretty special and pretty rare, it seems.

Find some cars for those '65 blocks!
Thats been my thought the whole time. Is it possible that this is one of those blocks used for dealer conversions? I wish it was'nt on the other side of the country, id love to check it out in person. Wish it still had the pad numbers on it.
 
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