Cyl. Head Casting Marks

[Hebert K.]

[Joe L.]

Re: Cyl. Head Casting Marks

Can anyone tell me the significance of casting marks on my 427 cylinder heads?
They are both P/N 3904391 (1967 427 square port)
One has a date of G96 (July 9, 1966), the other has a date of J106 (Sept. 10, 1966)
The G96 head has HIPERF X and GM2T cast in it, and the J106 head has HI-PERF (note hyphen), and GM1T cast in it. These are the marks I am wondering about.
These heads were on my car when I bought it and I think they are original.
Engine – P/N 3904391 (427/435) date – A97
Thanks.

Herbert-----

In the GM2T or GM1T, the "GM" denotes General Motors. The "1" or "2" (or other numbers) denotes the pattern number (the sand mold is made from a permanent pattern). Pattern numbers can vary widely and it's very common to have heads on the same engine which used different pattern numbers. In fact, if the pattern numbers are the same for both heads, that's the unusual condition. The "T" refers to the Tonawanda, NY foundry where all big block blocks and heads were cast until 1984.

By the way, there's quite a date spread between your cylinder heads casting dates and your block casting date. This is possible with big blocks but it's definitely not the "norm". What is the assembly date of your engine (from the engine code stamped on the stamp pad and beginning with a "T")?

[Hebert K.]

Re: Cyl. Head Casting Marks

Joe,
The code is T0112JE , also the vin number stamped on it matches the car.
Do you know if the (X) cast after the HIPERF denotes anything?
Thanks for the info.
Herb

[Joe L.]

Re: Cyl. Head Casting Marks

Joe,
The code is T0112JE , also the vin number stamped on it matches the car.
Do you know if the (X) cast after the HIPERF denotes anything?
Thanks for the info.
Herb

Herb-----


The "X" does have significance but I've forgotten what it is. Your engine assembly date is 3 days after the block casting date which is very normal. However, one of your heads was cast 6 months before the block was cast. With big blocks, this was possible and has been seen in other cases.

[Hebert K.]

Re: Cyl. Head Casting Marks

Thanks Joe,
It makes me feel better about the originality of the engine knowing such long lead times have been seen before.
Herb

[Patrick B.]

Re: Cyl. Head Casting Marks

Herb-----


The "X" does have significance but I've forgotten what it is. Your engine assembly date is 3 days after the block casting date which is very normal. However, one of your heads was cast 6 months before the block was cast. With big blocks, this was possible and has been seen in other cases.

I have heard that an "X" symbol on a casting was used to indicate that it was an early example of a particular casting so that attention to possible flaws would be maintained during machining and assembly. I think the 391 head castings first appeared in July 1966 making that head a very early example. As far as the time between casting a block and assembling and engine, three days would be typical of a small block but very short for a big block (about 4 weeks being typical with a spread between 3 days and 6 months observed).

[Wayne M.]

Re: Cyl. Head Casting Marks

While on the subject of casting letters/numbers, what does the "C1" mean, on this mid-May '65 big block ? (The line through the middle of the C is a depression, not raised).

[John H.]

Re: Cyl. Head Casting Marks

While on the subject of casting letters/numbers, what does the "C1" mean, on this mid-May '65 big block ? (The line through the middle of the C is a depression, not raised).

Wayne -

That probably identifies the molding line the block was poured on, like "conv1" or "conv2" seen on small-blocks.