3890462 heads

[Keith L.]

I found this thread while researching some heads my buddie has. They are both dated L 4 5. They have the double humps on the ends. He got them from a guy who had a knocking 327 they came off of. Is there any more info now about how early these were cast?


Joe Lucia
Re: Cylinder Head Casting Date

Kirk-----

I don't think that the GM casting #3890462 was still being manufactured in 1975. By that time, I believe that other castings had supplanted the '462' for SERVICE applications. However, if you're sure that the last digit is a "5", then it's unlikely that it represents 1965. I really doubt that the 3890462 had been released at that time. It's possible, I suppose, since it would be December, 1965, but if the date is actually 1965, then this head must be one of the very first 3890462 castings ever made. So, if it doesn't represent 1965, then it must represent 1975 and, perhaps, my notion that the 3890462 was out-of-production by then is wrong.

The interesting thing here is that if it was cast in 1965 at Tonawanda, the 1 digit year code was in common use at Tonawanda at that time. If it was cast in 1975 at Tonawanda, the 2 digit year code was in predominant use at that time. So, we get no help there in figuring this thing out.

[Joe L.]

Re: 3890462 heads

I found this thread while researching some heads my buddie has. They are both dated L 4 5. They have the double humps on the ends. He got them from a guy who had a knocking 327 they came off of. Is there any more info now about how early these were cast?


Joe Lucia
Re: Cylinder Head Casting Date

Kirk-----

I don't think that the GM casting #3890462 was still being manufactured in 1975. By that time, I believe that other castings had supplanted the '462' for SERVICE applications. However, if you're sure that the last digit is a "5", then it's unlikely that it represents 1965. I really doubt that the 3890462 had been released at that time. It's possible, I suppose, since it would be December, 1965, but if the date is actually 1965, then this head must be one of the very first 3890462 castings ever made. So, if it doesn't represent 1965, then it must represent 1975 and, perhaps, my notion that the 3890462 was out-of-production by then is wrong.

The interesting thing here is that if it was cast in 1965 at Tonawanda, the 1 digit year code was in common use at Tonawanda at that time. If it was cast in 1975 at Tonawanda, the 2 digit year code was in predominant use at that time. So, we get no help there in figuring this thing out.

Keith------


The 3890462 was not used in PRODUCTION until late in the 1966 model year. I still do not think that any were cast as early as 1965. My strong suspicion is that the year code reported as a "5" is actually a "6".

[William G.]

Re: 3890462 heads

Well...........not to attempt to throw a monkey wrench into this issue..........but I've got a 1966 with a 3890462 head on it with a cast date (clear as a bell, as us old timers would say) of March 30, 1966. Or said another way, C 30 6. I certainly would not say that an April build car is "late in 1966". I don't profess to being an expert but I don't believe in all sincerity that this engine has ever been apart. I wouldn't bet my life on it not ever having been apart but thin steel factory head gaskets are on both banks, the french locks are still on the exhaust manifolds and the acorn nuts still on the head pipe flanges. As I said my life is too valuable to me.........but still. In a factory setting as big as Chevrolet I'm sure a lot of things happened that don't fit the generally accepted rule.

[Joe L.]

Re: 3890462 heads

Well...........not to attempt to throw a monkey wrench into this issue..........but I've got a 1966 with a 3890462 head on it with a cast date (clear as a bell, as us old timers would say) of March 30, 1966. Or said another way, C 30 6. I certainly would not say that an April build car is "late in 1966". I don't profess to being an expert but I don't believe in all sincerity that this engine has ever been apart. I wouldn't bet my life on it not ever having been apart but thin steel factory head gaskets are on both banks, the french locks are still on the exhaust manifolds and the acorn nuts still on the head pipe flanges. As I said my life is too valuable to me.........but still. In a factory setting as big as Chevrolet I'm sure a lot of things happened that don't fit the generally accepted rule.

William------

A cylinder head cast on March 30, 1966 would not have ended up in a Corvette until mid April, 1966, at the earliest. In 1966 they only built Corvettes into July, 1966. So, a car built in mid April or later would certainly be classified as a "late 1966".

[Wayne M.]

Re: 3890462 heads

A. Colvin's Chev-by-the-Numbers says "...462 basically used from Jan '66 thru late May '67, although some sources show earlier casting dates"

Then, in discussing the predecessor # 3762461, he says: "The end of '461' production was approx. June 1966. Most applications used this head prior to Jan '66. Late in the '66 model year, the 3890462 head was released...."

[David L.]

Re: 3890462 heads

The earliest 3890462 cylinder head that I have seen was dated "C 1 6" (March 1, 1966).

Dave

[Keith L.]

Re: 3890462 heads

I will take pictures. I haven't seen the dates but He says it is clearly L 4 5 on both heads. Maybe he didn't have his glasses on but I will check them.

[Joe L.]

Re: 3890462 heads

I will take pictures. I haven't seen the dates but He says it is clearly L 4 5 on both heads. Maybe he didn't have his glasses on but I will check them.

Keith------

Given that it would be December, it's not impossible that the year was 1965. Like I said in the previous thread, they would have to be about the earliest 3890462 heads ever cast. It would be interesting to know what the pattern number was for the heads. For such an early-cast head, I would expect a LOW pattern number (like "1").

[Keith L.]

Re: 3890462 heads

[Joe L.]

Re: 3890462 heads

Keith------

Yes, the year is definitely a "5" for 1965. So, these must have been among the first heads of this casting number ever manufactured.

And, as I postulated, they do have a low pattern number.

[Keith L.]

Re: 3890462 heads

I have never really payed much attention to pattern numbers. How high would they typically go?

[Joe L.]

Re: 3890462 heads

I have never really payed much attention to pattern numbers. How high would they typically go?

Keith------


It depends entirely on the production quantity and production duration of a particular casting. I might also emphasize that interpretation of pattern numbers is far from an "exact science" and the very last thing I want to do here is "get something started" on this feature.

Basically, as I understand it, pattern numbers were issued sequentially from the outset of casting of a particular part number. However, the pattern remained in use as long as it was serviceable and was needed. Theoretically, the first pattern produced for a casting would be numbered "1". However, there may have been, say, five patterns produced coincidentally. So, all five would be used during the initial production run of the part. Thereafter, patterns would be added as necessary to accommodate increased production requirements OR to replace patterns no longer serviceable.

Consequently, one would expect low-numbered patterns to be used at the beginning of the life-cycle of a casting. However, it's possible that pattern number "1" could still be in use on the last day of the casting of a particular part if that pattern was still serviceable at that time. It's far less likely, though, that a high-numbered pattern (e.g. "48") would be in use at the beginning of the life cycle of a casting number.

[Keith L.]

Re: 3890462 heads

Thanks Joe. So would the odds be that a cars heads would have the same pattern number or is it just chance?

[Joe L.]

Re: 3890462 heads

Thanks Joe. So would the odds be that a cars heads would have the same pattern number or is it just chance?

Keith------


Actually, it's unusual for any particular engine to have both cylinder heads of the same pattern number. For instance, in my example of a case in which there are 5 patterns in use at the start of casting for a particular part, that would mean that there was only a 20% chance that the 2 heads used on any engine would have been manufactured from the same pattern. As time goes on and more patterns come into use, the chances are even less.

The original GM #3927186 cylinder heads on my original owner 1969 small block are of pattern numbers "25" and "31". My engine was built in mid-August 1969 and the 3927186 had been in production for about a year at that time. Of course, the 3927186 was a widely used and a no-doubt high production item for the 1969 model year.

[David L.]

Re: 3890462 heads

Joe,

By a pattern number I assume you mean the number after the "GM" (like the "GM 4" in Keith's photo). If so, I always believed that to be the mold number.

Dave