Engine serial number format?

[Bob W]

What is the format for the engine serial numbers on a 4 cylinder Henry J or Allstate car? How do you know if a vehicle has the original factory installed engine?

Thanks!
Bob Westerman
52cj3a@gmail.com

[Fid]

The engine number is stamped into the block, on the passenger side, upper front. It is also listed on the engine tag/plate attached to the same side of the block. The two numbers should match.
According to the 1955 edition of "Motors" repair manual, the Henry J engine numbers started with 3500000 for the four cylinder (1951) and 3000001 for the six cylinder (1951) and carried through for the 52-54 models. It does not mention an ending number. Since there were about 123,000 Henry Js produced, with a few more six cylinder models than fours, the numbers would likely range to approximately 3560000 for the four cylinder and 3060000 for the six.
The 1951 Henry J used Autolite starter, generator, coil and regulator. The 1952-54 Henry Js used Delco-Remy starter, generator, coil and regulator so if you have a 1951 with Delco-Remy parts or 1952-54 with Autolite parts, the engine is likely not original. This doesn't mean it's bad or won't work right, it just means it's been replaced. On a 50+ year old vehicle, that is not uncommon.
Hope this helps.
Best of luck.

[Bob W]

Thanks very much for the reply! I have been keeping track of Supersonic engines that are swapped into Willys Jeeps. There are more Supersonics in Jeeps than I would expect to see. The engine serial numbers I have documented are between 3501493 and 3558675 so I guess they were all removed from a Henry J.

Did KF dealer replacement engines have the same serial number format?

Thanks,
Bob

[Fid]

I don't have any information on the KF replacement engines and number. Perhaps someone will come on who has that info.  A lot of four cylinder Henry Js were converted to six cylinder models by restorers. There was one problem though - if you replaced a four cylinder engine that did not have overdrive, with a six cylinder engine that did not have overdrive, the rear end gearing is too low and it will actually perform worse than the four did. The correct trans/rearend combination is necessary for good performance.