1972 Engine Casting Code

[Glen C.]

I ran across an advertisment locally for a 1972 with "the very rare experimental M casting date." I can't find any reference to an M code in the reference books I own and I was curious about this. Can anyone fill me in?

Thanks,

Glen

[Terry M.]

Re: 1972 Engine Casting Code

I ran across an advertisment locally for a 1972 with "the very rare experimental M casting date." I can't find any reference to an M code in the reference books I own and I was curious about this. Can anyone fill me in?

Thanks,

Glen

Glen,

I take it you don't own the 1970-72 TIM&JG. I can cite you page(s) it is referenced on when I get home. However, I can assure you that the TIM&JG does NOT ... By The NumbersThe Corvette Restorer abouit it. A search of the C3 CD by "M code" will turn it up.

[Glen C.]

Re: 1972 Engine Casting Code

Terry,

I currently don't own those materials. My library is prety limited at the moment but growing. I did try a search prior to posting my inquiry but the threads I tried broght back nothing.

Thanks for the information. I'll check out the Restorer articles you mentioned.

Glen

[Kenneth H.]

Re: 1972 Engine Casting Code

Glen,

Try this link:

https://www.forums.ncrs.org/showthread.php?t=70516

In this thread you'll find two documents explaining the reasons behind the "M" code in the casting date. In a nutshell, it had to do with experimenting with changes to the manufacturing process of the blocks and not modification to the blocks themselves. While unusual to see an "M" code block casting date, it doesn't make them any more valuable than a standard dated block. The restorer article was from volume 27, #4, Spring 2001 titled "M was for mystery" written by Gene Gamache (not sure about the spelling). Also, note that "M" code casting date blocks were installed in all models manufactured by Chevy, and not just corvettes.

By the way, I have an "M" code block casting dated engine in my '70 LT1.

Thanks.

[Terry M.]

Re: 1972 Engine Casting Code

You beat me to it Ken because I am at work and the boss likes me to do some things for the company besides "surf the net.' That thread showed up on page 7 or so of my search. We talk about codes way too much here.

I knew one of you guys with a dog in this race would jump in.

[Kenneth H.]

Re: 1972 Engine Casting Code

I tried, but I couldn't resist, Terry.

Thanks.

[Michael G.]

Re: 1972 Engine Casting Code

You beat me to it Ken because I am at work and the boss likes me to do some things for the company besides "surf the net.'

It appears you need to get back to work and quit mess'n around "surf'n the net".

[Patrick B.]

Re: 1972 Engine Casting Code

Were the "M" codes used in place of the casting date, or do these blocks also carry a casting date?

[Terry M.]

Re: 1972 Engine Casting Code

Were the "M" codes used in place of the casting date, or do these blocks also carry a casting date?

Pat, the M is in the place where the date code is usually found. There are usually number(s) following the M which make it easy to misread it as a date code. According to the folks at Saginaw (or the folks who used to be at Saginaw given they were retirement age) those numbers gave details of what was changed on the cases, but about a decade ago no records existed regarding them. That was their story and they were sticking to it.

The documents posted not withstanding those same people told me that the changes could have involved configuration changes to the cylinder case. They were not willing to rule that out, however they did say that most likely the changes were to the chemistry mix (alloy) or temperature of the pour or changes to the composition of the moulds.