See Figures 1 and 2
There are several ways to identify the engine size, manufacturer and year. The first is by comparing digits 3 and 10 through 17 of the VIN plate with the VIN derivative which is stamped on the engine block.
If the 2 sets of numbers correspond, then it is safe to say that this is the original installed engine. The next thing to do is correctly identify the size of the engine by checking the 8th digit of the VIN plate and comparing the digit to the VIN chart.
On the V6 and all V8 engines, except the 307 c.i. (VIN Y) Oldsmobile carbureted engine, the serial number is found on a pad at the front right hand side of the cylinder block, just below the cylinder head. On the 231 c.i. V6, the number can be found on a pad on the left side of the cylinder block, where it meets the transmission. On the 307 c.i. (VIN Y) Oldsmobile carbureted engine, the number can be found below the front of the left exhaust manifold assembly.
The engines are also stamped with a number which identifies the assembly plant, the day and month produced and the engine type code.
Stick on labels are also used to identify engine unit number and code. The sticker also contains bar coding for in-plant identification.