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Question about "F" head 134 engine serial number.
Today in attempt to help identify the engine in my friend's 1948 JEEPSTER with body data tag of 4-63 77411, we found the engine to be an "F" head with serial number of: 4J384939, and casting number of: 807895.

I thought a 4-63 Jeepster had the "L" 134 Flat Head engine.
So we're thinking the "F" head engine has replaced the original flat head?

Any thoughts would be helpful.
odjeep

Checking the early Jeepster manuals and even the 1954 Motor's Manual it is pretty clear the L134 was used thru 1949 and F134 came in 1950. The six banger units kept running the L-6 for another year or two.

Thanks WES for conformation that the 4-63 should be the L-134 flathead,
Now if you please, can you advise the most likely casting number for the L-134 that would be found in a 1948 4-63 Willys JEEPSTER?
Aditionally what do you think the serial number range would look like?
Would it start with 3Jxxxxxx?
Thank you so very much for your knowledge and insight.
odjeep

641087. That 3J serial F134 came out of a 1954 to 65 CJ3B. If you visit the CJ2A page and review their data base you will see what serial group the 641087 would be closest to for 1948. Here's a link to the CJ3B page discussion on the upgrade from L134 to F134 but they seem to place it at the 1950 model year.
https://cj3b.info/Siblings/Jeepster.html Usually the Jeepster engines had a V prefix. I would investigate that as well.

Thanik you so much again WES K. So very helpful!
odjeep.