Casting date on 3963512 big blocks

[Mike E.]

When did the dating on 512 blocks change from a single digit for the year (9), vs. two digits (70)? Calendar year change, model year change, or random date? Thanks

[James G.]

Re: Casting date on 3963512 big blocks

Calender year.
It would have made the 69 - 70 change impossible given that the Chevelle changed model year before the Corvette & the first 1970 LS6 Chevelle was built prior to the last 1969 Vette being built.
I restored a car for a Foundry engineer who worked at Tonawanda in the 60's and 70's. He said in the middle of the winter sometimes there would be pallets of raw castings frozen in under ice until march/april.
I know there are a lot of 512's cast in Jan of 69 and not machined and assembled until as late as June.
Muncies may be the only part model year dated, is there anything else with date format based on model year?

That does make the 1969 model year odd... in that a muncie built after Oct 18th (iirc) has the A B C suffix codes so a Early Nov 68 built car could have the trans with a suffix and 9 model year. Then again the next Nov of 69 there is another batch of transmissions with later vins but also with the ABC. Cars built from aug to late oct of 69 would have A B C - the Early 69 cars built in calender 68 would not have suffix muncie codes.

[Patrick B.]

Re: Casting date on 3963512 big blocks

James-- I think the date codes on 512 blocks were moved from the side of the block to the bell housing flange around April 69. Did the year format change from one to two digits at the same time?

[Michael H.]

Re: Casting date on 3963512 big blocks

My 30,000 mile 71 Chevelle SS 454/365, block 512 is cast date G-9-70 ( July 9th ) by the bell housing flange. Assy date is T0908CPD. There was a 145 day UAW strike that closed all most all GM plants and many suppliers from Sept to Nov 1970. I've read that in Nov 69 the casting date was moved to the bell housing flange.

Mike

[James G.]

Re: Casting date on 3963512 big blocks

I've got a L 19 8 on the side,
A bunch of A 24 9 A 30 9 B 9 9 all on the side

I 5 9 on the flange