M 305 date code on 1975 333882 cylinder head

[Leonard M.]

Re: M 305 date code on 1975 333882 cylinder head

Terry, The Restorer story you refer to, as I recall was; "M for Mystery" by

Gene Gamache

. The NCRS link to that story does not work.
I had a 1972 with a M code block and although it is unusual, no one seems to care and trying to explain what it is makes a conventional dated casting better to own.
https://www.forums.ncrs.org/showthread.php?50906-M-code-block&highlight=mcode%20saginaw&uid=4876
Apparently the numbers have nothing to do with a date.

""M"-Coded Blocks: There is one exception to the normal block casting date convention that has been observed: some blocks have been seen with "M" cast codes. Research by the Saginaw Metal Casting Operations of GM Powertrain Division has found that these "M" codes are not date codes, but actually a foundry code used to indentify parts that were made to evaluate a casting process change. After evaluating the parts, the blocks would either be destroyed or released into production. There is no way to determine the date an "M"-coded block was poured."

[Kenneth B.]

Re: M 305 date code on 1975 333882 cylinder head

Ken this is helpful...For the sake of clarification, what you write has two interpretations is it 1. or is it 2. or 3.?

1. I was in the foundry/pattern business for almost 50 years & I guarantee that it is a date code and not a Foundry logo; or
2. I was in the foundry/pattern business for almost 50 years & I guarantee that it is a date code and not a Foundry (plant) logo; or
3. I was in the foundry/pattern business for almost 50 years & I guarantee a date code is not a foundry logo.

This statement suggests that it was a date code to track a day of bad castings, so they could be retrieved and destroyed. This makes sense, but then how to interpret what M 305 means?

M was not for bad castings but to check new tooling or repairer ones. To me it means a test casting made the thirtieth day of X month in a year that ended in a 5

[Terry M.]

Re: M 305 date code on 1975 333882 cylinder head

Terry, The Restorer story you refer to, as I recall was; "M for Mystery" by

Gene Gamache

. The NCRS link to that story does not work.
I had a 1972 with a M code block and although it is unusual, no one seems to care and trying to explain what it is makes a conventional dated casting better to own.
https://www.forums.ncrs.org/showthread.php?50906-M-code-block&highlight=mcode%20saginaw&uid=4876
Apparently the numbers have nothing to do with a date.

""M"-Coded Blocks: There is one exception to the normal block casting date convention that has been observed: some blocks have been seen with "M" cast codes. Research by the Saginaw Metal Casting Operations of GM Powertrain Division has found that these "M" codes are not date codes, but actually a foundry code used to indentify parts that were made to evaluate a casting process change. After evaluating the parts, the blocks would either be destroyed or released into production. There is no way to determine the date an "M"-coded block was poured."

Thank you Leonard.

The thread you linked to in your post has the documents from Chevrolet and Saginaw in posts #4 and #5. Those are the documents we used in developing the statements in the 1968-69 and 1970-72 TIM&JG regarding these M codes.

The question now becomes -- and I think it is the question Tom R is asking in the OP -- does this also apply to Heads and intake manifolds???

Tom, correct me if I am wrong.

[David B.]

Re: M 305 date code on 1975 333882 cylinder head

Suggest the first sentence of thread #1 stating Alpha Codes run from A to L is INCORRECT! at least with regards 1975 V8 cylinder heads.

J = September
K = October
L = November
M = December

If you are still a non believer, some additional research might be a good thing!

[Mike E.]

[Tom R.]

Re: M 305 date code on 1975 333882 cylinder head

Terry...you wrote:

The question now becomes -- and I think it is the question Tom R is asking in the OP -- does this also apply to Heads and intake manifolds???

Tom, correct me if I am wrong.

My query above:

I'm assuming this would carry over to cylinder heads as well. The M code is a foundry code used to evaluate a change in the casting process according to the note. The Julian code of Nov 1st, 1974 fits well for this E17 (February 17, 1975) built Corvette.

I want to use this for the 75-77 TIMJG revision but wish to confirm accuracy before I assume the above is the case...thx

Jack Morocco sent me the NCRS article "M was the Mystery" but apparently from what I read here, it remains elusive. attached is a letter from another link that provides some information about the use of X and the three digit numbers.

M Tag.pdf

[David B.]

Re: M 305 date code on 1975 333882 cylinder head

Good question Mike, appears GM had to skip but cannot say when, will try to find answer. If anyone still has a 1975 camshaft, date behind second journal should show similar alpha numerical sequence (although no year shown). Note all engine components are not necessarily date coded the same.