On late model flatheads without the bell housing cast into the block (1949-1954), the number is located on the right-rear corner of the intake manifold gasket surface. It is visible with the cylinder heads and manifold on the engine.
See > http://myflatheadford.com/5988-2/
Flathead Date CodeOn late model flatheads without the bell housing cast into the block, there is a code stamped on the right rear corner of the intake gasket face of the block which will give you the manufacturing date of your flathead Ford or Mercury. You can see it with the intake manifold and heads still on the engine.
It consists of a series of a letter, a one or two digit number, and a second letter. The first letter is the month. The number is the day, and the second letter is the last digit of the year.
The letter code is M=0, G=1, B=2, L=3, A=4, C=5, K=6, H=7, T=8, R=9, S=10, E=11, F=12.
G 20 B would be an engine manufactured on January 20, 1952.
As for the other styles of blocks, most folks can identify the engine series if not the exact date of assembly. If you can’t, refer to one of the flathead books available or one of the other flathead web sites.
I should credit Flathead Jack’s catalog as my first source for this information, although I have now seen it in several places.
Please remember that it is possible, even likely, that the year the engine was assembled will be the year before the car’s model year. Also, I have heard, but never verified, that if Ford rebuilt an engine, they changed the date code to reflect the rebuild. I have seen flatheads on which the date code appeared to be missing, although I suspect this is an artifact of time, rust,