1970 LS-5 Water pump

[Scott Sims]

What is the correct water pump for a March built 1970 Corvette 454 with AC? I've been told three different numbers, the most "votes" for the 960.

Thanks,
Scott

[Jack H.]

Re: 1970 LS-5 Water pump

Per the '70-72 Judging Guide:

"1970 and 1971, up to at laeast s/n 1400, Mark IV's use water pump casting number 3856284, however, 1970 Corvettes as earl as s/n 2077 use casting number 3992077. There is clearly some overlap of Mark IV casting numbers in 1970 and 71...."

[Scott Sims]

Re: 1970 LS-5 Water pump

Jack, thanks for responding. I am attaching an email from a person (Mockauto@aol.com) who firmly believes that the NCRS manual may in error or at least not totally correct. The other source that also states the 960 is correct is Roberto Luis, a source with the 1970 Corvette Registry. To add to that another water pump rebuilder firmly believes that the 960 is correct. Below is Mockauto@aol.com response to me:

Scott,

I have been doing the Corvette water pumps since 1978. I was the source for the Corvette water pump information for Alan Colvin. The NCRS judging manual is WRONG! The latest casting date on the "284" water pump is April 1969 and the earliest date on the "077" water pump is August 1970. After April 1969, the 1969 Corvettes with 427 engine started using the 3940960 water pump and all 1970 Corvettes with 454 used the "960" water pump. Attached is a picture of a NOS "960" water pump with B3.70(February 3,1970) date code.
Bill Mock #93
PS - I wrote the original NCRS judging rules for 1965-67 Corvettes in the late 1970's after 1963-67 were recognized by NCRS. Up to that point NCRS was for only 1953-1962 Corvettes.

[Thad L.]

Re: 1970 LS-5 Water pump

Scott, do you have the large fan with the tips? If so, what is the date on the fan---D70? thanks Thad

[Scott Sims]

Re: 1970 LS-5 Water pump

Thad, I do have the large fan with tips but the car is not here with me as it is having a correct engine rebuilt for it. I can check tomorrow and get back to you. I'm going to visit the "patient" tomorrow.
Tell me about the D date you referenced. I yearn to learn. The problem, if it is a problem, is that the car was bought with a 1977 454 in it but the components from the original engine were transferred to the 1977 block including a 1971 077 water pump. All of the AC and alternator brackets are there including the fan blade which surprised both my mechanic and me. Two months ago I found a 1970 Corvette 454 long block with a CGW suffix. This started my quest to get the right parts.

Scott

[Thad L.]

Re: 1970 LS-5 Water pump

I have an April 1st car with a tipped fan and date of D70. Sounds to close to build date---BUT a couple of years ago I sold my March built car with the tipped fan and It also had a date of D70. So just trying to learn if the D is the month or something else. Both cars were never hit and even had there origional fan clutches and radiators! Oh there were both LS-5 cars with A/C.
Let me know what you find. Thanks Thad

[Tony H.]

Re: 1970 LS-5 Water pump - Why 960 shortlived?

Scott,
Very interesting. I've run into similar discussions regarding water pumps for 1970 big blocks. My Corvette (July 70) had a 1971 077 pump. I believe it was the second owner who had the original water pump changed out at a Chevy dealer. (I don't recall if I have the receipt, I think I do.) Anyhow, with your story of a 1971 077 pump, that makes me wonder why the 960 was so shortlived. The answer might make for an interesting Restorer article...

[Scott Sims]

Re: 1970 LS-5 Water pump - Why 960 shortlived?

Tony, it all started after I found that 1970 Corvette 454 long block. My '70 has a 1977 454 in it and it drove me nuts to know it was a..a...a truck engine. Anyway, the engine I bought was eerily close to the build date of my Corvette, 03/70, and came out of a 1970 LS-5 convertible wrecked in 1981. The engine was stored all those years. Even the pad stamp was only 9 days apart from the build date of my car. So I set about to find the correct starter and did, a rebuilt 1108429 and date code 0A03. I already have an NOS fuel pump and 1100884 alternator (2). I even found some vintage, original flash chrome valve covers. Then came the water pump dilemma. As I am a member of the 1970 Corvette Registry I contacted Juliet Page and told her the story. She asked me to poll the LS-5 owners on the Registry and find out what they have on theirs and what they believe or know to be correct.
Regarding the tipped fan blade I have not seen an actual D code stamped on any I've seen. However, I have information that fan blade #3969926 was used until April of 1970 and then blade #3993889 was used.

[Joe L.]

Re: 1970 LS-5 Water pump

Jack and Scott-----

Personally, I don't think that a single 1970 Corvette was ever built with a 3856284 waterpump. I think that casting was completely out of production by that time. If I saw a '284' pump with a very late 1969 or 1970 casting date, I might believe otherwise. However, I've NEVER seen such a pump.

1970 Corvettes used waterpump GM casting #3940960. I doubt that any other casting was originally used for any 1970 Corvette. In fact, late 1969 Corvettes also used the 3940960 pump. To me, that pretty much rules out the possibility that any '284' castings ever carried over to the 1970 model year.

It's possible that the 3992077 pump casting was used for VERY late 1970 Corvettes. I doubt that, though. The 3992077 casting was, primarily, designed around the 1971+ waterpump configuration. However, it could have been used for the 65-70 waterpump; it is interchangable on a functional basis.

One of the reasons that I believe that a 3856284 casting may be found on a 1970 Corvette is that the '284' casting is, by far, the most common of the 65-70 big block short leg waterpump castings. If one were to purchase a rebuilt waterpump, especially in the 70s or 80s, for a 1965-70 Corvette, the chances of getting a '284' pump casting was VERY HIGH. I'll bet there was about a 99% chance that's what you'd get. The '284' casting was used for ALL 1965-68 big blocks, Corvette and otherwise. There were LOTS of this casting manufactured. However, the later short leg castings were used ONLY for Corvette and some MD/HD truck applications. So, those castings are FAR less common.

Anyway, I expect that it was through the "rebuilt" route that these "original" 3956284 castings found there way onto 1970 Corvettes.

[Scott Sims]

Re: 1970 LS-5 Water pump

Thanks to both of you. Joe, I just sent you an off board email. Thanks to reputable informational sources here and elsewhere I bought a rebuilt 960 pump dated correctly to the build date of the block. Elsewhere sources being Bill Mock (Mockauto@aol.com), Larry and Adam (RestorParts@nuvox.net), and Roberto Luis in Argentina (bobluis@yahoo.com). Check out Roberto's Corvette Web site, in Spanish (http://www.geocities.com/bobluis).

I have not seen the NCRS manual on this subject but I am told it does not address the 960 pump nor does the 1968-1982 Corvette Parts Interchange Manual. In the short time I have been searching I have not seen a 284 pump casting date past April 1969 nor a 077 pump any earlier than August 1970. I am told that Chevrolet by the Numbers does list the 960 pump as a 1970 Corvette 454 pump.