can anyone explain this

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Jan 13, 2008 | 10:56 AM

67COPO

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From: stormville ny

can anyone explain this

my 66 corvette block is date coded d 21 6, has heads that are date coded c 28 6, and d 13 6 which is a good thing because the car was built around april 29 1966 .
my problem is the heads casting number is 3890462 which according to all the books are from 67.
i was thinking that once they decided to change the heads for 67 they used up what 66 casted heads they had and retooled the machinery and started using 67 heads but with the correct build date.

Jan 13, 2008 | 10:40 PM

Stingray1967

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From: Twin Cities, MN

I agree with your guess that they put 67 heads on a late 66. Wouldn't be the first time that something from an adjacent year made it onto the "wrong" car. Although, I show the last 66 being built on July 29, 1966. That would be a big gap from April to late July to be putting all 67 heads on the 66s.....

Jan 14, 2008 | 06:22 AM

67COPO

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From: stormville ny

i agree that would be a big gap but am confused because of the build dates on the heads.i was unable to find any other year except 67 with that casting number being used.

Jan 14, 2008 | 08:45 AM

vark_wso

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From: Sun Prairie WI

My (original) '66 has 462 heads, but it was built on July 13th. Latest NCRS Tech Info & Judging Guide (4th edition) states "... very late 1966 cars may possibly have factory installed cylinder heads with casting number 3890462...".

Jan 14, 2008 | 08:48 AM

67COPO

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From: stormville ny

question on date codes for 3890462 heads

i did a search of 3890462 heads on the forum and found 2 posts of these heads one having a c 22 6 build date and the other having a f 14 6 build date.
wish i could find out what is the real story on the casting and date because i'm going to be putting my 66 coupe for sale and would like to have the correct answer when someone asks me about the casting number being a 67 .

Jan 14, 2008 | 09:16 AM

provette67

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From: Kirtland Ohio

This is a little confusing but here goes.According to Alvin Colvin's Chevrolet By The Numbers "#3890462 was basically used from Jan. 1966 through May 1967,although some sources show earlier casting dates.In march or April 1967 the #3917291 head was released and there seems to be some possible minor useage overlap.There have been early #3890462 heads with late March 1966 in some applications"

Jan 14, 2008 | 12:19 PM

67COPO

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From: stormville ny

from what everyone has said so far i'm going to believe that these heads are the originals for my car.if anyone has any other info please post it or pm it to me i would be greatful.
thanks to everyone who posted on the subject.

Jan 14, 2008 | 12:31 PM

Stingray1967

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From: Twin Cities, MN

How long have you owned the car? Do you know if the motor has ever been apart? I'm told that the original GM head gaskets had "GM" stamped on them on a tab that you could see without pulling the heads. If this is true, and your engine has this, it is likely that the motor has never been apart.