1964-1990 Oldsmobile V8 engine information
[ Thanks to Joe Padavano, Bob Barry, Jeff Easton for this information ]
In 1964, Oldsmobile came out with a new 330 cid small block engine. In 1965 the 400 and 425 cid big block engines were introduced. Over the years other displacements were added. The Olds 455 was introduced in 1968, it was developed from the Olds 425, which was a tall-deck version of the 330 engine design. Both of which replaced the 394 cid V-8, which was developed from the design introduced in 1949 as the 303 cid "Rocket" V-8. Production of big blocks ceased in 1976, although some were used (not necessarily in cars) in the 1977 model year. Production of small blocks ceased in 1990.
The big and small block engine types are almost identical, with the big block having about a one inch higher deck than the small block. The bore centers are the same, the only differences between the small-block and big-block Olds blocks are the deck height (9.33" and 10.625", respectively) and the main journal size (2.5" and 3.0", respectively); the diesel 350 used the BB size mains, however. All small blocks have a 3.385" stroke; the displacement varied by increasing the bore size.
 Parts interchangeability
Many internal parts interchange: flexplate and flywheel, engine mounts, oil pan, front cover, water pump, bellhousing (also interchanges with modern Cadillac, Buick and Pontiac), oil pump and pump driveshaft, rocker arms and fulcrum (except early 330), cam and lifters, harmonic balancer, cam bearings, timing chains and timing gears. Heads will basically interchange, except manifold ports may not align. Early engines used both 39 degree and 45 degree lifter angles along with two different lifter diameters. Because of these differences, cams and lifters will not exchange between engines with different angles and lifter diameters, obviously. In 1980 push rods were changed to a larger diameter tip, from 5/16" to 3/8". Because of this changes were needed to the rocker arms and lifter cups.
 Engine names
The engines were sometimes named, and this was printed on the air cleaner label or sticker. "Rocket" was used early on and continued to be used intermittently throughout the years. The mid 1960's 425 was known as the "Super Rocket". Some featured "Ultra High Compression" on their labels. The high performance 350 and 400 were named "Ram Rod" in 1968-'69; the 350 became the W-31.
 Visual cues
The large oil fill tube on the front of the engine, sticking up from the timing chain area, is a dead giveaway that it is an Olds engine. The distributor is found at the back of the block and it does not go through the intake manifold, but right into the block. Also the spark plugs will be above the exhaust manifolds with no need for heat shields.
The valve covers have a distinctive shape. Straight running front to rear, with an arc connecting each end of the two lines, to define front and rear. From their sealing surface, the covers are curved as they meet their top. The top of the covers are flat, like someone cut off the curved top.
The thermostat cover/radiator hose has a special molded in bypass pipe for the waterpump.
The block code and/or head code can give you an idea, but some codes cover many years. The casting number is usually nearby. Other than that, there is no method of determining the year of manufacture of an Olds block. If the engine's original factory paint is still intact a small block will be gold or blue, while the big blocks can be red, green, blue or bronze. Late model 307's are flat black. However, since paint is easily changed, it should be used as supporting evidence, not as absolute indication of engine lineage.
The day of the year of manufacture is the big number right by the distributor hole.
The VIN derivative stamping or engine unit number is on the front of the block, on the driver's side, just below the cylinder head. The pad is part of the engine and will indicate the year of manufacture, but that is usually rusted beyond recognition, and it can be changed by restamping. Basically it IDs the car in which the motor was originally installed. It can provide some circumstantial info but not a positive ID.
The VIN derivative on '68-up blocks doesn't tie directly to the type of car it was installed in (unless you have some way to unambiguously trace the last six digits of the VIN), however it can provide some indirect evidence. For example, if the production plant (third place in the VIN derivative) was one at which no 442s were built (KC, for example), then it obviously isn't a 442 motor. Of course, you have no way of knowing for sure that the heads were originally installed on that block or not.
For example, what this proves is that it could be a W-30 short block, but it could also be a Toronado motor. W-30s were only built in Lansing, so if the VIN derivative had shown some other production plant, you would have positive proof that it was not a W-motor. Of course, if the motor is still in the car and the car is positively a W-30 and the last six digits of the VIN match, then it is a W-motor.
If the engine was replaced under warranty, the pad may be blank. Rubbing alcohol and Q-tips help to remove the grime and grit from the stamping.
 1964-'67 V-8 Engine:
Code is stamped on the right cylinder head. Unfortunately, this only applies to what was originally the driver's side head. This code consists of a prefix letter (330 V-8=T (1964-'65) or W (1966-'67), 400 V-8 = V), then a production sequence number, followed by a suffix code letter (L = Low compression, E = 2-bbl export, G = High compression, H = 4-bbl export). A 2-letter code on the oil filler tube identified the engine.
 1968-later V-8 Engine:
Have the last six digits of the VIN number, the year of the block, and the assembly plant stamped on the driver's side of the block below the cylinder head. A 2-letter code on the oil filler tube identified the engine.
You can use the VIN derivative number to ID the year. For 1968-up blocks, this number is located on a pad just below the cylinder head on the front left side of the engine. This number will be stamped on a machined pad on the front driver's side of the block, just below the deck surface. Typically it will be covered with a power steering bracket or something, below the number one spark plug location.
This number should take the form of "35Mxxxxxx" where:
3 = Oldsmobile division.
5 = year of manufacture (8='68, 9='69, 0='70, ..., 4='74, 5='75, 6='76, etc).
M = location of manufacture (M = Lansing, B=Baltimore, X = Kansas City, Z = Fremont, CA, etc).
xxxxxx = last six digits of VIN of car that motor originally came in (original car's sequential production number).
The letter indicating factory must match the letter in the sixth position of the car's VIN (it should also, of course, match the factory indication on the body data plate - in other words, for a Lansing-built car, the sixth place in the VIN would be an "M", the body data plate should indicate "LAN", and the third place in the engine ID should also be an "M").
Now, obviously this doesn't provide all of the information you're looking for, but you do get something. Year of manufacture is nice to know. Additionally, the manufacturing plant may provide some info as to the motor's original use. For example, if the letter is an "X", that signifies Kansas City, which only produced full size cars (88 and 98). Framingham (the letter escapes me at the moment) built only A-bodies. Lansing, on the other hand, built all Olds car lines (surprise), so an "M" doesn't tell you much.
If the motor has a number stamped which doesn't match the above, it's a non-original motor from another car. If it doesn't have any number stamped at all, it could be one of two things. First, it could be a dealer-installed factory service block, which would come without a VIN derivative. The dealer should have stamped the new block with the VIN derivative, but may not have. The other possibility is that it's a 1965-'67 block (i.e., a short-stroke 400 or a 425), as these motors did not have the VIN derivative stamped on the block. Note that obviously this latter option can be checked by looking at the block casting letter ("D" for the 425, "B" or "E" for the 400 - as opposed to "G" for the correct 1968 long-stroke 400).
Some blocks before 1977 have their ID cast above the right hand center freeze plug, e.g. "D" for 425, "F" for 455. Olds didn't cast the displacement into the side of the blocks until they went to the lightweight design in 1977. The 1977 and newer blocks will have the cubic inche displacement (i.e. 403, 455, etc.) cast in large raised numbers right above the passenger side center freeze plug. The 307 will be in liters (5L), and a diesel engine will have the letters "DX" on it. The engine VIN letter will also be cast into the side of the block. Note that the 260 blocks sometimes have the last 3 digits of the casting number cast there, "355", which could be rather misleading.
The VIN in 1972 and newer cars tells you what engine the car came with.
The number stamped on the oil filler tube is the engine unit code. The first number indicates the year the engine was assembled and the remaining numbers refer to the sequence number of the engine assembly (for identification at the engine assembly plant). This number has no link to any of the VIN data of the vehicle and does not contain any codes that identify the engine size.
From the factory, the oil filler tube had a sticker containing two letters which indicated components (carb, etc.), model application (Cutlass, 88, etc.), and other configuration items (timing, CA emissions, etc.). See the chassis manual for a complete list of available configurations. In 1973 and later, the factory did tune the emissions packages to the specific models that an engine might be installed in, but before that, in general terms, most engines were virtually the same across all model lines.