Identification of Big Block Heads

[Bob A.]

Your help in identifying the following "Big Block Heads" would be greatly appreciated. I was unable to find this information in the archives.

(1) GM1T, HIPERF X, 3873858, B 8 67
(1) GM1T, HIPERF X, 3873858, A256

Many Thanks!

Bob Adams

[Joe L.]

Re: Identification of Big Block Heads

Your help in identifying the following "Big Block Heads" would be greatly appreciated. I was unable to find this information in the archives.

(1) GM1T, HIPERF X, 3873858, B 8 67
(1) GM1T, HIPERF X, 3873858, A256

Many Thanks!

Bob Adams

Bob-----


The GM #3873858 heads are rectangular port, closed chamber heads originally used for 1966 model year SHP applications. These included 1966 passenger car and Corvette with L-72 and 1966 Chevelle with L-78. The head with the "B 8 67" casting date (February 8, 1967) must have originated as a SERVICE head since they weren't being used in PRODUCTION by that time. The other head could have been one used in PRODUCTION for any of the above-described applications or it could also have started life as a SERVICE head. No way to say, for sure, and it's a moot point, anyway.

Both heads were apparently cast from sand molds made from the same pattern which is what the "GM1" refers to. The "T" refers to the Tonawanda, NY foundry where most big block parts were cast until 1984.

[Bob A.]

Re: Identification of Big Block Heads

Joe:
Would these heads be considered an OEM pair that could be used on a 1966, 427?

[Joe L.]

Re: Identification of Big Block Heads

Joe:
Would these heads be considered an OEM pair that could be used on a 1966, 427?

Bob-----

FUNCTIONALLY, they are identical. Casting number-wise, they are correct for any 1966 L-72. However, date-wise, the head cast in 1967 would not be correctly dated for any 1966 Corvette L-72. The other head would be correctly dated for a 66 with L-72 manufactured from about early February 1966 through early July, 1966.

Tip: if one used the 1967-cast head on the driver side, no one would ever be able to discern that it was incorrectly dated. If the car had a build date as described above and the 1966-dated head were used on the passenger side, "all would be well".

[Joel F.]

Re: Identification of Big Block Heads

Bob,

Is it possible you made a typo with the dates? It is very unusual for a head to have a complete year. In the past I have seen heads with no year, or with the the last digit of the year (a "6" in your case).

Joel

[Bob A.]

Re: Identification of Big Block Heads

Joel:
You were right on the money, I incorrectly read one of the identificaton numbers. The A256 was correct. The other number that I posted, B 8 67, should have been B 8 6, just as you suspected. What is your opinion now?
Thanks and Best Wishes!
Bob

[Joel F.]

Re: Identification of Big Block Heads

Bob,

Those heads would have probably been installed on a car built late Feb, probably thru the end of production. That said, NCRS judging does not look at head casting dates, so you are fine using these on any 66 SHP big block.

Joel