EDIT: Sorry I would not have replied if I had seen Bruce's post above but his post was done while I was typing mine.

I don't believe anyone was arguing that the hardness of one block vs another was the issue. It was when you (or someone) were correlating hardness changes to composition changes being one in the same. These things do not always go hand in hand. Like Bruce (or whoever it was) mentioned; you would have to do a statistical analysis of a sample from each sample of block. Even then if the mixture time was not evenly mixed you could have higher deposits in one side of a block or even mix to mix or pour to pour. But at the end of the day the same composition is used. My guess is that GM did have quality control for each batch and maybe even throughout each batch if I had to guess.

Thanks.

Please stick around... together we might figure this out.:beers:

Anyone here track original engine cars that are reported to have the "born with" block as part of a data base?

It would be interesting to see the balance of reported original DZ-302 blocks stated as being original to the car.

It is about 7.5 months of production for both the 618 and then the later 010 so it might be worth a look.

I had a 69 Block 4 bolt main, 3970010 Casting Number. I was going to use this block to build a 69 Z-28 302 Clone engine. It had the 010-020 cast numbers also with that strengthen 4 cast strips as shown in a picture about this topic. It had the correct 302 Cast Number caps too. It just was not a DZ stamped block. Hope we find out more info about these numbers.

Think warranty mitigation... and the number of CE blocks GM did not want to continue to pay for...

WOWWWW…I posted this question and since have been traveling and just got back to it.

Read through the whole thread. Did not mean to start all this.

Thanks for all the replies.

Without stepping on any toes, To me it’s simple…

Norwood plant manager (posthumous) and superintendent of engine plant chimed in.

Nuff said ��

Thanks SYC . Best site out there. Folks here actually lived it !!