Anybody out there own a 69 with an M code instead of a block casting date.

 

Hi Jim,
I believe the M signifies a block that was a 'test' cast at the foundry. The test often involved the process used in the casting.
These 'test' blocks were sometimes destroyed, but also were sometimes released for use in production.
Regards,
Alan

Added: I just realized that might not be what you're asking.... no, I don't have one.

 

Hi Alan:

Thanks for your reply. I wanted to see if anyone out there owned a 69 with the M designation. I have heard of a couple & they seem to be early 69 cars. I have a 69 convertible with the M code, original motor, Oct 68 car. I wanted to see if there were others & compare notes.

Thanks
Jim

 

Hi Jim,
Could these M cast blocks early in 69 production have anything to do with the change from 327 to 350 cylinder cases and tests to get that accomplished successfully?
Regards,
Alan

 

ttt

 

M coded blocks were not exclusive to early cars. I owned an October '69 build L46 with an M-code engine. I believe they can be found in '70's as well.

 

Thank you for the reply. So your build date code on your 69 trim tag was O_ _ correct? Was it a coupe or convertible?

 

My friend wrote an article for the NCRS restorer magazine in 2001 about the m codes. "M was for mystery". He still gets inquiries about the M codes.



To date he has found M codes in early 69, 70,71 &72. And they were not restricted to 010 blocks.

When engineering wanted to test a new process in the production of blocks, they would have a number of them built with the letter M cast into the block where the casting date normally went. This block was "special".

The number to the right of M signified what was done to the block as an improvement. He could not find records at the foundry that would tell what each number represented. It could have been a change in the total resin used, mold pressures, iron temps, whatever and probably will never be known.

Once it was determined that the change worked the remaining blocks were sent out to the production line. If the process failed then the remaining blocks were destroyed.

If you want, send me a pm with your address and I will mail out a copy of the information he gathered.

Gene said he would gladly take your info for his records too.

 

PM sent

 

PM sent

 

Keep in mind 69s were assembled in two Octobers. October 68 (B) and October 69 (N). None were assembled in May due to the strike.

 

Hi Mike:
Thanks for the reply. Oct 68 is actually C & Oct. 69 is O.

 

ttt

 

I own an early '70 LT1 M code engine. The block casting date is "M108".

Ken

 

Hi Ken:
Thanks for your reply, I have a 69 300hp M27. I'm trying to determine how many of these there may be. I know of a couple 69's so far & a few 70's . What was you body build date?

 

Jim,

First, one of the past National Team Leaders on the NCRS site is keeping a log of all of the "M" code engine blocks and I believe mine was about number 14 or 15 when I submitted the info last year. I think that Gene's article referred to there being about 12 at the time of the writing of his article.

As for my LT1, the pad is V0I20CTU (January 20) and the trim tag is B05 (February 5). The VIN is 02856 and I did get the NCRS dealer delivery service document showing a build date of February 5.

Also, keep in mind that "M" code blocks were released to Flint for installation into ALL Chevrolet models, not just Corvettes. If you do a search on the Internet you'll eventually come accross discussions concerning Camaros and "M" code engine blocks.

In addition to Gene's article in the Restorer magazine, there's also a letter from the Saganaw foundry that one of the members here provided to me addressing the issue of "M" code castings. If you don't have it let me know and I'll send it to you. If I can figure out how to post it, I will.


Thanks,

Ken

 

Hi Ken:

Thanks for your reply. If the foundry letter you are referring to is from Roger Wilson, supervisor of the pattern shop, I do have a copy of that letter, as well as Gene's article. Its a very interesting subject. I don't think there were many 69's that I have heard of so far. Any further info on this subject would be appreciated.

Thanks You
Jim

 

Jim,

Yes that's the one I'm talking about. Do you have the cover letter signed by William Nichols that goes with it? After posting yesterday I took a look at what I have and found an article in a Saginaw newsletter dated October 6, 2000 that is written by Ross Howay (sp) that discusses the "M" code castings. There's not much info in it and it's not a very good scan but you're welcome to a copy if you want it. Let me know.

Ken

 

Did the M code engine have an 'M' in a square? Someone said it was a Marine engine so I never thought about it any. If so we had one here at the shop with a 6 after it. I have pictures of it since I had never seen one like that. I don't remember if I took pictures of the front pad or not.

 

The M would appear on the back of the block, on the passenger side where the bell housing would bolt up. This is normally where the block casting date would be. Do you know what the block casting number is, & the stamped info on the front pad?

Thank You
Jim