1968 buick gs-400

[Guest Jim Pellino]

How can I tell if the motor is original ?

[NTX5467]

Tracking "originality" of engines can be variable . . . depending upon the model year, the brand of the vehicle, and just how much information is on the engine block itself.

For example, there can be casting numbers on the various parts of the engine assy, plus stamp numbers on the distributor, carburetor, alternator/generator, etc. There are several Buick-related websites which can have the casting number information for you, plus intake manifold and cylinder head casting numbers.

There usually is a digit in the VIN which designates "engine", but whether this is a letter or a number is variable. In the case of a 1968 vehicle, having the original Protect-O-Plate in the back of the owners manual can have a LOT of information on it, by itself, as this plate was used to stamp warranty repair orders when the car was new. More information on it than in the VIN, in some cases! How to decode the Protect-O-Plate information was usually in the front of the Buick parts books, back then. Had to consult the service manuals to find where the stampings were on the block and on the cylinder head, too, as to engine size.

There were ID plates on the autmoatic transmissions, but IF the trans has been to a mass-rebuilder, that information is usually discarded as they put their OWN ID numbers on it.

The rear axle should have a string of ID or "birth certificate" numbers on the rh axle tube, facing the front of the vehicle. Again, the decode for this is in the parts book covering the particular brand of GM vehicle.

Chevrolet engines are usually highly traceable, due to their stamp codes on the front of the rh cylinder head deck surface (on V-8s). In later years, the last part of the VIN was even stamped there, too.

You might post the same inquiry in the V-8 Buick website forum as well as the BCA Forums also hosted by the AACA.

Take care,

NTX5467

[Guest Commodore]

OK The first website will tell you where to find the engine serial number and the second will tell you what it means. On these cars the engine serial number was the same as the car's VIN.

Buick Engine Identification, where to find the numbers

1968 BUICK GRAN SPORT Information Specifications Resources Pictures

[joe_padavano]

OK The first website will tell you where to find the engine serial number and the second will tell you what it means. On these cars the engine serial number was the same as the car's VIN.

Buick Engine Identification, where to find the numbers

1968 BUICK GRAN SPORT Information Specifications Resources Pictures

Actually, not quite the same. The engine and trans had a nine character VIN derivative stamp (the actual VIN was 13 characters). The first character of the VIN derivative will match the first character of the VIN of the car it was originally installed in (should be the number "4" in this case, signifying Buick Division). The last eight characters of the VIN deriviative will match the last eight of the car's VIN. The second character of the VIN derivative is the model year and should be an "8" for 1968. The third character is the assembly plant. The last six are the car's build sequence number. Starting with the 1968 model year, the Feds required VIN derivative stamps on major components (block, trans, and frame) in an (ill-fated) attempt to curb auto theft and "chop shops".

By the way, THIS is the definition of "numbers matching" - the VIN derivative stamps actually MATCH the car's VIN.

[NTX5467]

What Joe describes might sound a little unusual, BUT it relates to how the various components were routed from their respective assembly facilities to the various assembly plants AND to be warehoused at the plants for the various cars they produced. Usually, there were different brands of the same platform of vehicle built in the same plant AND assembly line. Then, with the production sequence being known, they could be sequentially sent to the assembly line as the particular "build sequence" vehicle arrived at the installation location on the assembly line. In some cases, there were also "color code" stripes or daubs of paint for easier identification of the various types of transmissions (for example) so the line workers could look for "a color" rather than having to read a piece of paper attached to the component.

There could also be color daubs or smaller stripes applied to signify "final checks" by the line worker supervisors and such. Like being sure a particular bolt is torqued to a particular value on a steering linkage part, or similar. These "color codes" are not related to the "color code ID marks" mentioned above, though.

Enjoy!

NTX5467

[joe_padavano]

I'll just add to the prior post that the reason for a VIN derivative stamp on components instead of the whole VIN is that the four characters left off of the VIN derivative are simply the model and body style (characters two through five of the VIN). Since the engine doesn't really care if it goes into a Skylark four door or a GS convertible, those numbers aren't really important to the VIN derivative. The division (Buick), model year, assembly plant, and sequential build number of the car were the important pieces of data. These were not duplicated during the model year - in other words, there would not be two cars with the same VIN derivatives. Sequential build numbers were duplicated among the various assembly plants, but then the assembly plant code would be different, so again the VIN derivative would be unique to each car.

[73supreme]

Hello Joe,

I am trying to find info on frame ID's. I have a 1968 4-4-2 convertible with a rotted frame. It may be easier to replace it altogether. I gather that the A body from the four divisions from 1968 to 1972 would fit. However, I cannot find any written resource tables to help ID the frames while shopping. Mine is almost legible. Top line; 3908665 (S) 42X,

Bottom line 9  26, so far. I read your text and was hoping you could elaborate and recommend a source table. Thank You, Ed

[padgett]

Also virtulaly every component in a GM car of that period will have a date code somewhere and should be inside the six months prior to the build.

 

ps no GM car ever came down the line with an R-59 battery (never say never but would be unusual, plant would not even have one).