I recently found and cleaned a GM aluminum waterpump with the following number "raised" on the front, 3975928. How do you read the date code on this piece and any idea what years that number represents. Thanks in advance.
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Re: Joe Lucia, Waterpump pt. no. question!!
That's the casting number - the casting date should be adjacent, in the month/day/year format; probably not a production pump with a 397- casting number (1969-era number) if it's aluminum. -
Re: 63 FI, Waterpump pulley question!!
I have two waterpump pullies each with its own number. One must be correct.
One starts with number 862 and the other with 377 or 337? I think the 377xxxx
is the one, what might the other one fit? They both provide the same mechanical
function.Comment
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Re: Joe Lucia, Waterpump pt. no. question!!
George------
GM #3975928 is the casting number for the big block short leg aluminum waterpump. This pump was released for SERVICE in January, 1970 under GM PART #3977630. It was originally scheduled to be used in PRODUCTION for the 1970 Corvette LS-7. However, that engine was still-born, so the 3977630 waterpump was never used for any PRODUCTION engine. GM later catalogued it as the SERVICE waterpump for 1967-69 427 HD applications (i.e. L-88/ZL-1). However, it was NEVER originally used in PRODUCTION for ANY of those applications. All of those, including the PRODUCTION ZL-1s, used a cast iron waterpump. The 3977630 didn't exist in time to be used for any PRODUCTION ZL-1 as many folks incorrectly surmise (I mean, why would GM build an engine with aluminum block, aluminum heads and aluminum intake manifold and use a cast iron waterpump? Well, they DID, and it's because they didn't have a short leg aluminum waterpump in their parts bin at the time those engines were built for PRODUCTION). However, some SERVICE ZL-1 engine assemblies sold from 1970 to about 1972 may have been equipped with it.
In 1983 the GM #3977630 was discontinued and replaced by the GM #14058915. As far as I can tell, that pump is identical to the 3977630. I'm sure there is some difference but I can't tell what it is. Both pumps use the 3975928 casting. The GM #14058915 is still available in SERVICE to this very day.
Incidentally, although original 1969 ZL-1s did not use an aluminum waterpump, my "ZL-1" will have such a pump. I mean, why build an engine with aluminum block, aluminum heads, and aluminum intake manifold and then use a cast iron waterpump? Just because GM did it, doesn't mean that I have to do it. I'll be using the 3975928 casting pump, too.
Usually, the examples of the 3975928 casting that I've seen have the XX.XX.XX date format that many GM aluminum castings are seen with. Other systems may have been used, though. I do believe that the foundry that cast the piece changed over the years, although the tooling was transferred from one to another.In Appreciation of John HinckleyComment
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Re: Joe Lucia, Waterpump pt. no. question!!
Thanks for the in depth response. Under the raised casting numbers are four spamped numbers "5421" under those numbers are a series of less pronounced stamped numbers "34017". Under the 3 oclock rib is a cast tag that has 252001 on it. The impellers inside the pump indicate that the pump has been around awhile. I considered using it on a aluminum head 67 aplication, the GM casting numbers jump out at you and the 397.... was from that ara. The history lesson was great.
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