Correct cylinder heads for a very late 1967 L68

[Eric T.]

If a car is a very late 1967, with an assembly date of June 19, 1967, are cylinder heads with casting numbers 3917215 considered correct if the heads' casting date are before the engine assembly date?

The heads have matching casting dates of June 7, 1967 and the engine assembly date is June 8, 1967.

The heads are not bossed or tapped.

Thank you very much for any info!!!

-Eric

[Joe L.]

Re: Correct cylinder heads for a very late 1967 L68

If a car is a very late 1967, with an assembly date of June 19, 1967, are cylinder heads with casting numbers 3917215 considered correct if the heads' casting date are before the engine assembly date?

The heads have matching casting dates of June 7, 1967 and the engine assembly date is June 8, 1967.

The heads are not bossed or tapped.

Thank you very much for any info!!!

-Eric

Eric------


Yes, the 3917215 and otherwise as you described would be considered correct for a very late 1967 with L-36 or L-68.

[Mark E.]

Re: Correct cylinder heads for a very late 1967 L68

Was it possible back then to assemble an engine one day after casting it? I'm wondering what process lead times GM had back in the day.

[Michael S.]

Re: Correct cylinder heads for a very late 1967 L68

@Mark, thats what i'm thinking. i do not think a head can be cast one day then machined and built, then shipped to the engine plant to be build. i would think a week at least would be needed.

[Patrick B.]

Re: Correct cylinder heads for a very late 1967 L68

I have seen small blocks cast the same day as the assembly date, so I do not think it is impossible for a day old big block head to have been machined and ready for assembly.

[Eric T.]

Re: Correct cylinder heads for a very late 1967 L68

If a car is a very late 1967, with an assembly date of June 19, 1967, are cylinder heads with casting numbers 3917215 considered correct if the heads' casting date are before the engine assembly date?

The heads have matching casting dates of June 7, 1967 and the engine assembly date is June 8, 1967.

The heads are not bossed or tapped.

Thank you very much for any info!!!

-Eric

Thanks to all for the responses so far. I guess I need to further refine my question; would anyone anticipate a point deduction for these heads, in the engine as described? Thanks again!!

[Tim G.]

Re: Correct cylinder heads for a very late 1967 L68

Getting near to the end of production it seems possible that the short time between the two could have happened. The temp sender location changed from the intake to the head in 1968, so they may have been speeding things up to get ready for that change. Of course, the casting number and date of the head are not reviewed during judging. As long as there is no hole for a temp sender, you're ok I would think.

[Pancho T.]

Re: Correct cylinder heads for a very late 1967 L68

Since the date and casting number are covered by the valve cover they will not be seen during judging

[Joe L.]

Re: Correct cylinder heads for a very late 1967 L68

I have seen small blocks cast the same day as the assembly date, so I do not think it is impossible for a day old big block head to have been machined and ready for assembly.

Patrick------


Yes, this has been seen for both blocks and heads for small blocks and, in that case, the castings had to travel from Saginaw to Flint for machining.

For big blocks, it was even easier. The Tonawanda foundry and Tonawanda engine plant were co-located-----right next door to each other. This was the case throughout the Corvette big block period.

By the way, in the late 80's the foundry was shut down and big block castings were done at Defiance, OH and shipped to Tonawanda.

[Patrick B.]

[Eric T.]

Re: Correct cylinder heads for a very late 1967 L68

Eric——I am surprised that you found these heads to be not bossed. The 840 heads used on late 67 435’s had the bosses. They were simply not drilled and tapped for the temp sensors..........There was no need for them since simply not drilling and tapping them made them equivalent to 802 heads for use on 67 engines. Look again for the bosses. Post some pictures. If they actually have the bosses, they would be visible to judges. Would you have to remove the valve cover to demonstrate that the castings were dated correctly? I don’t know. I believe that these heads are original to your engine, but they may be new to 67 judges.

Patrick:

I may be getting my terms confused. I guess what I'm trying to say is there is nothing drilled or tapped for the temperature sensor, in the head. I thought the boss was the female thread through the head wall - I'm probably wrong. Can someone explain the correct terminology?

[Joe L.]

Re: Correct cylinder heads for a very late 1967 L68

Patrick:

I may be getting my terms confused. I guess what I'm trying to say is there is nothing drilled or tapped for the temperature sensor, in the head. I thought the boss was the female thread through the head wall - I'm probably wrong. Can someone explain the correct terminology?

Eric------


A boss is a feature of a casting. Usually and certainly in this case, it will be a raised area of the casting that's intended for some sort of subsequent machining and, possibly, tapping. Usually, the boss is designed so that there will be sufficient depth for machining and tapping which might not be the case if a boss were not present. For example, in this case there would not be enough material thickness in the head to drill and tap for a temp sender if a boss was not provided. Most pre-1968 heads did not have the boss because the temp sender was in the intake manifold (which had a boss for this purpose).

[Eric T.]

Re: Correct cylinder heads for a very late 1967 L68

Eric------



A boss is a feature of a casting. Usually and certainly in this case, it will be a raised area of the casting that's intended for some sort of subsequent machining and, possibly, tapping. Usually, the boss is designed so that there will be sufficient depth for machining and tapping which might not be the case if a boss were not present. For example, in this case there would not be enough material thickness in the head to drill and tap for a temp sender if a boss was not provided. Most pre-1968 heads did not have the boss because the temp sender was in the intake manifold (which had a boss for this purpose).

Got it. These heads DO have a boss, but they are NOT tapped. Will they cost me points?

[Joe L.]

Re: Correct cylinder heads for a very late 1967 L68

Got it. These heads DO have a boss, but they are NOT tapped. Will they cost me points?

Eric------


They should not. All castings of GM #3917215 should have the boss and that casting number is accepted for very late 1967 L-36/L-68.

Actually, heads of this casting number would have to have been used for very late 1967. While 3917215 is generally considered a 1968 cylinder head, all 1968's used the cylinder head mounted sending unit. So, the heads you have with the untapped boss could not have been used for the 1968 model year. That only leaves late 1967.

[Tim G.]

Re: Correct cylinder heads for a very late 1967 L68

I don't think so. That part number head that is not taped would have been made in the small window of time before they were taped for a 1968 and used in a 1967. I'd embrace the uniqueness of the heads on your car. This is one of those cool idiosyncrasies.