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This is stamped on the block I couldn't get a good picture: 3970010
That's the engine casting number at the back on the driver's side. GM used that casting number from '69 through all of the 70's in two and four bolt main versions in a variety of cars, vans, and trucks, including the Corvette. Arguably the most common block ever made by GM, but it's a good block, IMO. There should be a block date code on the back ledge of the block just behind the cylinder head (cylinder #8) on the passenger side.
GM freely used engine blocks that were available on the assembly line back then, which may or may not reflect the actual year of the car in went into. e.g, the assemblyman may have used a block made in '70 in a '71 car, then stamped the the VIN pad on the front of the block to match the VIN number of the car. Without those being intact, you can't be completely sure.
Last edited by Corvette-ZL1; Feb 13, 2023 at 10:50 AM.
That VIN puts you in the last week of production of April 1971. The block was cast March 26, 1971 so it looks like it could be the original block as that date code lines up nicely with your car’s date but it is possible someone found a replacement block as the 010 blocks were used on many Chevrolet (and Pontiac) cars then. If you are willing to pull the valve covers, you can see the head casting numbers and date codes there as well.
[QUOTE=69L88;1606269213]That VIN puts you in the last week of production of April 1971. The block was cast March 26, 1971 so it looks like it could be the original block as that date code lines up nicely with your car’s date but it is possible someone found a replacement block as the 010 blocks were used on many Chevrolet (and Pontiac) cars then. If you are willing to pull the valve covers, you can see the head casting numbers and date codes there as well.
[researching prior posts for help I came across this from last year. Hope someone can help. My 71 engine was rebuilt by previous owner. Numbers decked off front #2 plate. My engine date, I think, is “L90” (see photo) which I think is December 9, 1970. Couple of questions 1) does this date make sense with a build date of August 1970? 2) what is the “3” in the photo?
A casting date code cannot be later than the production date of the car. That block was originally installed in a late December 1970 or early January 1971 build of a 1971 model year car.
A casting date code cannot be later than the production date of the car. That block was originally installed in a late December 1970 or early January 1971 build of a 1971 model year car.
