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First of all, that's not a "stamp". Stamped numbers are inset and applied after the part is cast. The VIN derivative is a stamp. These are raised casting numbers that are integral with the casting.
Second, despite what you may read on the interwebs, the large raised "3" is a mold number and has no direct relationship to the year or any other date. Below is a dealer technical bulletin that clearly identifies this as the mold number.
Third, the small number is the day of the year. The VIN derivative stamp will tell you the model year, which lets you figure out the day of WHICH year that julian date number refers to.
Second, despite what you may read on the interwebs, the large raised "3" is a mold number and has no direct relationship to the year or any other date. Below is a dealer technical bulletin that clearly identifies this as the mold number.
Thank you for the mold number info. I was aware of the VIN derivative stamp.
Just a friendly FYI, I did not get the info from the interwebs. The information I used is from page 28 of “The Good Old Days, Oldsmobile 1964 thru 1972 A bodies” by Michael J. Siedlik.
From page 29:
Your information is good to know.
Last edited by ericisback; Sep 13, 2022 at 07:08 AM.
Thank you for the mold number info. I was aware of the VIN derivative stamp.
Just a friendly FYI, I did not get the info from the interwebs. The information I used is from page 28 of “The Good Old Days, Oldsmobile 1964 thru 1972 A bodies” by Michael J. Siedlik.
Be even more suspicious of a book that gets it's info from the old Oldsmobile FAQs on line. That's just sheer laziness (and theft) on the part of whoever published that. Here's an FYI back to you: Don't trust third party documents like that. Get your info from factory literature if at all possible. Most of what I've read (both in books and online) is incorrect, and frequently is just copying bad information that someone else wrote.
The oldest rumor of this number I remember is that it revealed the nickel content of the iron
I believe there is a larger version of it on the back of the block behind the flywheel.
The ludicrous part about the "F number" related to nickel content myth is that all 1964-up Olds motors have an "F number" on the back, but the nickel content link only applies to 455 blocks. WTF? This one long predates the interwebs, so we can't blame it for this. Also the "headers don't fit Supremes" myth.
