M 305 date code on 1975 333882 cylinder head

[Tom R.]

A set of 1975 cylinder heads 333882 have a date code of M305 and M285 but the alpha codes run from A to L. The C3 manuals include a note about the M code used in the date code for the block, 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

cylinder head_338882.jpg

[Mike E.]

Re: M 305 date code on 1975 333882 cylinder head

Tom, you are right on. I had a 72 with an original M head on it.

[Tom R.]

Re: M 305 date code on 1975 333882 cylinder head

Tom, you are right on. I had a 72 with an original M head on it.

Thanks Mike. Good to know there is another head out there, somewhat concurrent with the 75 and the M code.

[David B.]

Re: M 305 date code on 1975 333882 cylinder head

Not into C3, but curious what the C3 manual note says about the M code. (M code is also Lansing).

[Tom R.]

Re: M 305 date code on 1975 333882 cylinder head

Here's page from the 75-77 TIMJG revision, that only adds the cylinder heads to the description used in early C3 TIMJGs. What do you mean..."M code is also Lansing?"

1975-77 _TIMJG_M Casting Doe_10Jun20.pdf

[David B.]

Re: M 305 date code on 1975 333882 cylinder head

In 1973-79 there were 28 GM numerical Plant code letters. M was the letter for the Lansing plant. Reading the link explanation , the cast M does not appear related.

[Tom R.]

Re: M 305 date code on 1975 333882 cylinder head

So what would make this more correct? Its either one of two scenarios. It currently states and, according to your source, is unrelated:

Research with Saginaw Metal Casting Operations of GMPowertrain Division found that these are not dates, but are a foundrycode used to identify castings made to evaluate a change in the castingprocess.

I'm not clear what your point is but suspect that the note over rationalizes the M casting and its no more than the GM plant code for Lansing. Or is the objection that is has nothing to do with "a change in the casting process?"

The M in the casting represents the Lansing plant where the block/cylinder head was cast

[Paul B.]

Re: M 305 date code on 1975 333882 cylinder head

...when Ed McComas judged my '74' engine at the Corvettes@Carlisle Regional there that year in '96, he found out my left cylinder head is dated "V xx3". He looked at me and said, "What month is "V" in 1973?" Wonder if the "V" here has any thing to do with Flint, like the engine suffix's?

[Terry M.]

Re: M 305 date code on 1975 333882 cylinder head

...when Ed McComas judged my '74' engine at the Corvettes@Carlisle Regional there that year in '96, he found out my left cylinder head is dated "V xx3". He looked at me and said, "What month is "V" in 1973?" Wonder if the "V" here has any thing to do with Flint, like the engine suffix's?

My guess is that the V he saw was part of an M.

That said, WTF was he doing looking at cylinder head dates? We don't do that, and both of you should have known that. Neither of you are rookies.

[Kenneth B.]

Re: M 305 date code on 1975 333882 cylinder head

I believe they were Foundry test castings to check new tooling. As they made thousands of caastings they could pick these out to check quality. If they were cosmedicaly & deminsiomaly correct they were sent to the machinig factory. They would not waste a good casting.

[Kenneth B.]

Re: M 305 date code on 1975 333882 cylinder head

My guess is that the V he saw was part of an M.

That said, WTF was he doing looking at cylinder head dates? We don't do that, and both of you should have known that. Neither of you are rookies.

MY MY someone is a little cranky today. LOL Is the stay at home order getting a little old. May be it was not being judged at a NCRS meet.

[Terry M.]

Re: M 305 date code on 1975 333882 cylinder head

MY MY someone is a little cranky today. LOL Is the stay at home order getting a little old. May be it was not being judged at a NCRS meet.

I'm not cranky, Ken just POed that judges and owners don't know their limit. That's why I intend to have my 1969 judged when the car is finished. I want to be on the other side of the fence again.

I am pretty sure that was an NCRS meet as a demonstration of how NCRS judges cars. Another reason for me to get worked up.

[Patrick H.]

Re: M 305 date code on 1975 333882 cylinder head

I'm not cranky, Ken just POed that judges and owners don't know their limit. That's why I intend to have my 1969 judged when the car is finished. I want to be on the other side of the fence again.

I am pretty sure that was an NCRS meet as a demonstration of how NCRS judges cars. Another reason for me to get worked up.

Terry,

Did you judge at that one in Carlisle?
I did. Still have the t-shirt.

PH

[Terry M.]

Re: M 305 date code on 1975 333882 cylinder head

Terry,

Did you judge at that one in Carlisle?
I did. Still have the t-shirt.

PH

I can't recall and the T-shirt pile is way too tall. Lol. Besides a T-shirt from 1993 would no longer fit me. Time for a T-shirt quilt.

Stay safe.

[Kenneth B.]

Re: M 305 date code on 1975 333882 cylinder head

I'm not cranky, Ken just POed that judges and owners don't know their limit. That's why I intend to have my 1969 judged when the car is finished. I want to be on the other side of the fence again.

I am pretty sure that was an NCRS meet as a demonstration of how NCRS judges cars. Another reason for me to get worked up.

Well if that was the case its crazy to have a judging demonstration with pulling off valve covers. Just was trying to pull your chain as you are always so calm not like me. So your going to the dark side of judging. Never heard of saw anything like it at the meets.