Buick assembly plants stamped the vehicle identification number (VIN) and engine code into the top side of the engine block.
On the ’65 nailhead engine, the VIN is stamped on the driver’s side, top front, just in front of the valley pan cover. It should correspond to the serial number that is on the VIN tag in the driver’s door jamb, on the car’s title and on the Protect-O-Plate literature (if it is still included in the glove box). This is what is referred to as a numbers matching engine, meaning that it is the same engine that was installed when the car was assembled.
It should read something like this 5K119589 and the VIN tag would then read 444675K119589.
On the passenger side, top front, just in front on the valley cover pan is stamped the engine code. It should have two letters and three numbers — for instance, LR305. The “L” indicates the year 1965. (“J” was used in 1963, “K” in 1964, “M”in 1966, etc.) The next letter (“R”) indicates the model of Buick, in this case the ’65 Skylark Gran Sport. The subsequent three numbers represent the production number. In the 1965 Skylark Service Manual, page 0-2, it states that the Gran Sport engine shall be identified by the “LR” code which will appear upside down when viewed from the front. However, contrary to the service manual, many of them were stamped right side up. This engine code should also appear on the Protect-O-Plate, which is stamped at the factory and affixed to the back page of the Protect-O-Plate booklet. The Protect-O-Plate would also have a second plate attached by the dealer to include the new owner’s name and address.
Now for the rare, unusual and unexplained . . . there are a few documented 1965 Skylark Gran Sports that left the factory with a numbers matching “LT” stamped engine code. A “LT” engine is identified as a 401 engine built in 1965. An “LT” engine block is identical to a “LR” coded 401. “Documented” in this case means that the VIN stamped on this “LT” block corresponds to the VIN tag and title and also appears on the Protect-O-Plate. The “LT” code should also appear on the 1965 GS Protect-O-Plate.Although the engine code is not included on the original window sticker, the original window sticker does have the collaborating VIN.
Here are photos of the VIN number and engine code locations:
VIN Number Location – Drivers Side
Engine Code Location – Passenger Side
The Registry is attempting to gather as much information about this issue. Hopefully there may appear a pattern or possible answer to how and why some have a documented “LT” code contrary to protocol. The most logical explanation for this is simply ‘human error’. A mis-stamped factory engine block from the 1960’s is not that unusual. Including this engine code information on your registration is greatly appreciated.