From:Dave Hennessey
Subject:RE: RE: title question Date:Fri Nov 22 10:28:51 2013
Response to:18972
The short answer - yes - the engine number is the "vehicle identification number" (VIN).

Before 1981, vehicle manufacturers used whatever numbering scheme they wanted, and affixed the number where ever they wanted - often just a plate riveted to the driver's door.

These "serial number plates" usually had the manufacturer name (e.g. Chevrolet Motor Division), a "body style" (some code for Corvette, Bel Air, Corvair - and the answer is yes! - etc.), and a sequence number.

Harley stamped the year-model-sequence "serial number" on the engine, as they had done since the early days. This was stamped just before the bike went out the factory door. To my knowledge they continued this until standardized VINs were mandated for 1981.

I'm not sure on the Hummer-series (Mutt - help!), but on bigger Harley engines, there was a casting code on the bottom of the engine halves. This had the year and a sequence number - for when the engine cases were cast. These should match on both halves, but the sequence number has NO relation to the "serial number". But the casting year should be the the same, or one year prior, to the one in the serial number.

Indians (at least in 1949, I've only owned one) stamped a number in both the engine and frame. This included a year/model code, and a sequence number. The sequence number was the same on both engine and frame, but the "year/model" code was slightly different on the engine and frame. So they should have "matching numbers".

Chevrolets had an engine code on the block at the upper front of the engine. For Corvettes only (I've also only owned one of those), the sequence number on the door was also stamped next to the engine code on the block - so they had matching numbers. They also had a "plant/model" casting on the engine block, and a year/month date code cast into the block. Lots of cross-checks to see if your Corvette is truly original.

More than you wanted to know...

From what I have seen and read, there were no VIN numbers on the frames of the lightweights - everything was on the engine.

Mutt has a thread on frame numbers here:

Were all the lightweights titled off the motor number ? Did the frame and motor numbers match ?