[John Brown]

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Small Block Chevy Engine Block Identification


General Engine Block Specifications
While 6 different bore size blocks have been produced, the small block engine can be classified into 3 bore sizes and 3 main bearing sizes. 283 blocks (3.875" bore, 2.3" main), 302/327/350 blocks (4" bore, 2.3" or 2.45" mains), and 400 blocks (4.126", 2.65" mains). In 1968 the main bearing saddles were increased in size from 2.3" to 2.45".

CID Year Bore Main Cap
262 1975 3.671 2 bolt ONLY
267 1979 - 81 3.500 2 bolt ONLY
305 1976 - 96 3.736 2 bolt ONLY
307 1968 - 73 3.875 2 bolt ONLY
327 1968-69 4.001 (2.3" main) 2 bolt
350 1968-88 4.001 (2.3" main) 2 bolt
265 1994 4.001 (2.45" main) 2 bolt
302 1968-69 4.001 (2.45" main) 4 bolt
350 1968-96 4.001 (2.45" main) 4 bolt
400 1970-72 4.126 (2.65" main) 4 bolt
400 1973-80 4.126 (2.65" main) 2 bolt

Notes: 2 bolt ONLY means what it says. You will NOT find a 4 bolt 305 block (made by the factory). Period. Otherwise 2 or 4 bolt can mean either design...



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I would hate to trust this as reliable information when the 68 and later 327's and 350's had large journal cranks, and this page incorrectly lists them as small journal. Who knows what other information might be incorrect.

Not doubting the messenger, just the message.