[Terry M. Hunt]

My 66 GTO was built 3rd week in March. Driver side cylinder head has a date code of C 2 8 which I understand means the 28th day of March. Is that correct? Below the date code is 2093. I know 093 designates a 66 GTO cylinder head, but what is 2093 supposed to mean?

Passenger side cylinder head has a date code of C 88( or maybe 86---second number hard to read) I would not expect the two digit number to be higher than 31 since it represents the day of the month, so what does 88 mean? Below this date code is 209. What does that mean?

[johnta1]

Do you have a pic of the 2093/209?


The C88 is Mar 8, 1968
They didn't put a zero in front of the 1st 8.

[Terry M. Hunt]

Trying to get pics of these codes attached to a post for all to see. Both heads have 093 cast into their center exhaust ports, so how could one of them be cast in 1968?

[johnta1]

The last '8' is probably a '6'. They can be very hard to discern sometimes.
I just went by what you posted on the C88.
If it is C86 it would be MAR 3rd 1966
Also the C2'8' is probably C26 which is Mar 2nd 1966

[Baron Von Zeppelin]

John is right about the sometimes hard to distinguish date codes.
Except C86 is March 8 1966 , not March 3
Just to avoid further confusion.

093 were only cast in 1966
Later SR 77 and 093 were usually no casting ID - with hand stamp ID , if any.

[Terry M. Hunt]

Here are 2 pics showing the casting codes on my heads. So, the heads were cast on March 2 and March 8. Is that right?

[Baron Von Zeppelin]

Yes .

Some of the 65-66 389 blocks have very sloppy date codes too and can be challenging .

[Kenth]

I see C 2 6 and C 3 6 casting dates.

FWIW

[Terry M. Hunt]

Any idea what the 209 and 2093 digits are supposed to mean?

[Baron Von Zeppelin]

2 usually represented Pontiac , but I can't say for sure that's why it is there.
It's common though.
In later years with partial VIN stamps on engines and tranny's , they always start with a 2 (for PMD)

209 just missed getting the 3 installed into the mold.
Foundry guy might have dropped it , and let it ride.

[242177P]

Originally Posted by Kenth

I see C 2 6 and C 3 6 casting dates.

FWIW

I'll second that. It isn't very pronounced, but there's an indication
of where it's supposed to be open. And for that to happen in not
one but two places, well, that can't be a coincidence. When you
add the other head's date into the mix. I'm no gambler, but C 3 6
is a safe bet.

[Baron Von Zeppelin]

3 would be even tighter on the dating of the pair.
Whatever it looks like in person is close enough either way.

I've had pairs of 77's and 093's that were both the same day.
And some would be a week or so apart.

[Kenth]

Originally Posted by Terry M. Hunt

Any idea what the 209 and 2093 digits are supposed to mean?

They are partial cast part numbers of the 9782093 full cast production number.

[60sstuff]

This 093 head cast date is a no brainer.

As Kenth pointed out they are C 2 6 and C 3 6.
Nice matched pair indeed.