The engine ID number is stamped on this machined pad at the front (passenger side) of the engine. This code was stamped by the engine assembly plant. This particular stamping decodes as follows: V = Flint Engine Plant; 05 = May; 25 = 25th day of the month; C = Car; NR = 350 cid/300 hp (w/TH-350 tranny) for use in a '70 full-size passenger car. Note the lack of an engine V.I.N. number on this block – which means this particular engine was not installed in a chassis on the assembly line.
WHAT DO THEY MEAN? Simply put, the proper numbers can mean the difference between a solid investment and losing your shirt! Actually, in the present-day restoration marketplace a premium is placed on muscle cars equipped with their original drivetrains. This doesn't mean a 396 Nova missing the original engine is worthless – far from it – but all else being equal the car with the original engine will be worth more. If you plan on entering your car in concours classes at shows, the correct components are necessary if you hope to place well.
Notice there's a difference in the meaning of original and correct. Original means the car has the engine or drivetrain parts installed by the factory when the car was built. Correct means the various components (i.e. engine code, head castings, etc.) are the proper type for that particular model. It's not usually possible to determine if the heads or intake installed on a particular engine are the originals simply because they weren't serialized by Chevrolet. However, the date codes of these parts should precede the build date of the car by 1-3 months. This isn't an exact science, however, and some exceptions do exist.
Since the cylinder block is serialized it's possible to determine whether the engine (or the block, anyway) was installed on the assembly line. The engine code should match the codes used in a particular application, and the sequence number should match the last six digits of the car's V.I.N. Should is the key word in the above statement however, since there are rare cases where an engine can be considered original and not have a matching sequence number.
There have been instances where engines were replaced under warranty, and although the technicians were instructed to stamp the sequence number into the replacement block, this did not always happen.
Engines with complete assembly plant and ID codes, but no sequence numbers, are the result. If the engine in your car has a sequence number that doesn't match the last six digits of the V.I.N., it is almost certainly not original. These cars were mass produced, however, and mistakes did happen on rare occasions.
This big block does have the engine V.I.N. code stamped to the right of the engine ID number. This code was added at the final vehicle assembly plant.
Since the engine codes were stamped on a pad that is an extension of the deck surface, it is possible to remove the codes and identification numbers. This may happen during a normal rebuilding procedure (if a block is decked), or it can be purposely done by unscrupulous persons trying to pass off an unoriginal or incorrect block/engine to an unsuspecting buyer. That's why it's extremely important that all the pieces of the identification puzzle match. The engine codes and sequence numbers should match, the various casting numbers should be correct and the component date codes must precede the build date of the car (but not by more than a few months). If all these match, it's a pretty safe bet the engine is original. If any one of these is incorrect, the authenticity of the car can be seriously challenged.
NOT casting numbers Tom, STAMPED numbers, I know the difference
Edited by jeffs396, 29 October 2011 - 04:19 PM.