mainline666

Were engine blocks cast in "batches" with the same date code used on hundreds or even thousands of blocks? The reason I ask is because I've been looking a several 1970 big blocks that have the same casting date of L 18 9. Did GM fire up the oven and bake 5000 of these blocks with the same code on them?

scottyp99

Yes, GM made more than one engine block per day.


Scott

Alan 71

Hi ml,
On small blocks, (maybe big blocks too?), in addition to the casting date, there were also a 'pointer' that showed the shift, (Day-light, Twi-light, and Night), and a clock with a slotted head that was turned to show what hour of the shift the block was cast.
It would be interesting to see the shift pointer and clock slot on the bbs you've looked at.
Regards,
Alan

qtlow

Hi Alan, do you or anyone by chance know how to read those cast clocks? I see on the shift clock the engine in your photo was made during the twilight shift. I can see on the time clock dial the two dots on top which might indicate 12:00 but there are only a total of ten dots.
Is that because of ten hour work shifts meaning it was made the sixth hour of the twilight shift?
Just curious.

Mike Ward

Yes, 10 hour shifts.

bkvette3

Interesting, I did not know that. Thanks, guys.

mainline666

Happy to expose my ignorance on this topic. Yes, I didn't think they cast one per day, but how many would be produced with the same casting date? Would you expect to see engines built in Jan, Feb, March, e.g., T01s, T02s, etc., with the same cast date on the block?

The shift "timer" is something I didn't check (yet).

Mike Ward

All of them cast on that date.

scottyp99

Are you asking if they cast a gazillion blocks on one day, and then used them to build engines for a few months, till they ran out, and then cast a gazillion more in one day?


Scott

69 Chevy

I'd say one every 12 seconds could be considered a gazillion!

Mike Ward

What's the source of the statement you quoted- I think something's being taken out of context.

mainline666

Sort of. I was wondering if they set up a mold with casting date L 18 9 on it and then used that for days/weeks until they hit a certain number, or did they actually only cast blocks on that day with that number for the length of that shift?

Mike Ward

As Alan has mentioned above, the block contains the time of day (or night) when it was cast, not just the date. The only real reason GM went to this trouble was for quality and traceability purposes.

If you've found three cars with the same date block, that's an incredible coincidence or there's something funny going on. Fake casting numbers and dates are not unheard of- a little JB weld mixed with iron filings can do miracles.

Don Rickles

For reference..........These are the actual casting numbers/letters that were used. Notice the bar with the fonts, the characters were changed out before molding.



Regards,

WB

Easy Mike

L 18 9 would have been used only on that day and for all blocks cast during that 24 hour period. L 19 9 would have been the day following. L 17 9 the day before.

The foundries ran pretty much 24/7.

FWIW: Flint Engine assembled approximately 5500 small blocks per day. That means they had to have 5500 block castings from the foundry per day.

scottyp99

Engine blocks and stuff like that are cast in a process called sand casting:

http://en.wikipedia.org/wiki/Sand_casting

The mold that the part is cast in has to be destroyed in order to get the part out, so a new mold is built for each and every block produced. They don't just have a mold that they can keep using again and again. When they are making the mold, it is not a big deal to include the actual date of production, and even the time, in the mold. So, to answer your question, no, the date is the actual day that the block was cast.


Scott

scottyp99

If we assume the foundry cranked out blocks 24/7 at a constant rate, then the chances of having two blocks with the same casting date would be 1 in 365. I don't even know how to do the math to figure out what the chances of having 3 of them, but ya don't have to do the math to be able to see that it would be pretty long odds. About the same as 3 randomly picked people all having the same birthday.


Scott

mainline666

Ok, I'm edujumcated now. Many blocks cast in one day. Date changes every day.

Any issues with a mid-December cast on a big block with an assembly date of 5-Feb-70? I heard around 2 weeks is the norm, but this cast is right around Xmas time.

Mike Ward

Depends entirely on the sample size. The OP made no mention of how many he looked at.

7T1vette

The block casting process was a continuous-operation type of system. Each block needed a 'new' core set. It was just like any other production line system.