Water Pump Date Code Format - NCRS Discussion Boards

Water Pump Date Code Format

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • Mark E.
    Extremely Frequent Poster
    • April 1, 1993
    • 4528

    Water Pump Date Code Format

    My car's 3840960 water pump is stamped "L80 8". Or read upside down, "8 087"? The "L" looks more like an L than an upside down 7 though.

    It's on the driver's side where the date code is normally.

    How is this interpreted?

    I looked in the JG, but didn't find anything about how to read the code.
    Mark Edmondson
    Dallas, Texas
    Texas Chapter

    1970 Coupe, Donnybrooke Green, Light Saddle LS5 M20 A31 C60 G81 N37 N40 UA6 U79
    1993 Coupe, 40th Anniversary, 6-speed, PEG 1, FX3, CD, Bronze Top
  • Larry M.
    Extremely Frequent Poster
    • January 1, 1992
    • 2688

    #2
    Re: Water Pump Date Code Format

    Mark:

    Water pump ate coding is MDDY............where M is the month in alphabet letters, DD is the day of the month in numerals, and Y is the year is numerals. Example is C127 which translates to March 12, 1967.

    For your example the L= December, the 80 could be 30, and the 8 representing 1968 or perhaps 1978. Hope this helps.

    Larry

    Comment

    • Mark E.
      Extremely Frequent Poster
      • April 1, 1993
      • 4528

      #3
      Re: Water Pump Date Code Format

      Originally posted by Larry Mulder (20401)
      Mark:

      Water pump ate coding is MDDY............where M is the month in alphabet letters, DD is the day of the month in numerals, and Y is the year is numerals. Example is C127 which translates to March 12, 1967.

      For your example the L= December, the 80 could be 30, and the 8 representing 1968 or perhaps 1978. Hope this helps.

      Larry
      It really looks like L80 not 30, so that threw me. Still looks like 80, but you're probably right.

      Also, sometimes the letter "I" is skipped in month codes. So could L be November instead of December?
      Mark Edmondson
      Dallas, Texas
      Texas Chapter

      1970 Coupe, Donnybrooke Green, Light Saddle LS5 M20 A31 C60 G81 N37 N40 UA6 U79
      1993 Coupe, 40th Anniversary, 6-speed, PEG 1, FX3, CD, Bronze Top

      Comment

      • Joe L.
        Beyond Control Poster
        • February 1, 1988
        • 43211

        #4
        Re: Water Pump Date Code Format

        Originally posted by Mark Edmondson (22468)
        It really looks like L80 not 30, so that threw me. Still looks like 80, but you're probably right.

        Also, sometimes the letter "I" is skipped in month codes. So could L be November instead of December?

        Mark-----


        If it's "80", then it's a factory mistake. I kind of doubt it. I expect it's 30.

        As far as the year, the GM #3940960 waterpump was used in PRODUCTION only for later 1969 and all of 1970. So, I don't see one of these pumps being manufactured as early as 1968. Also, I believe this pump was out-of-production for SERVICE by 1978. So, I do not know what to make of the year.

        The "I" is usually not skipped for CASTING dates. It's skipped for many STAMPED-type date codes, though.
        Last edited by Joe L.; April 7, 2017, 10:57 PM. Reason: correct error
        In Appreciation of John Hinckley

        Comment

        • Mark E.
          Extremely Frequent Poster
          • April 1, 1993
          • 4528

          #5
          Re: Water Pump Date Code Format

          Thanks Joe.

          Maybe it's cast "L30 9" (Dec. 30, 1969), not "L80 8"? Too much paint.

          Attached Files
          Mark Edmondson
          Dallas, Texas
          Texas Chapter

          1970 Coupe, Donnybrooke Green, Light Saddle LS5 M20 A31 C60 G81 N37 N40 UA6 U79
          1993 Coupe, 40th Anniversary, 6-speed, PEG 1, FX3, CD, Bronze Top

          Comment

          • Joe L.
            Beyond Control Poster
            • February 1, 1988
            • 43211

            #6
            Re: Water Pump Date Code Format

            Mark------


            I'd say L 30 9 which would be December 30, 1969 which is within the period that I would expect 3940960 waterpumps to be cast.
            In Appreciation of John Hinckley

            Comment

            • Mark E.
              Extremely Frequent Poster
              • April 1, 1993
              • 4528

              #7
              Re: Water Pump Date Code Format

              Originally posted by Joe Lucia (12484)
              Mark------


              I'd say L 30 9 which would be December 30, 1969 which is within the period that I would expect 3940960 waterpumps to be cast.
              Thanks Joe. I like your date better for a June 1970 car.
              Mark Edmondson
              Dallas, Texas
              Texas Chapter

              1970 Coupe, Donnybrooke Green, Light Saddle LS5 M20 A31 C60 G81 N37 N40 UA6 U79
              1993 Coupe, 40th Anniversary, 6-speed, PEG 1, FX3, CD, Bronze Top

              Comment

              • Joe L.
                Beyond Control Poster
                • February 1, 1988
                • 43211

                #8
                Re: Water Pump Date Code Format

                Originally posted by Mark Edmondson (22468)
                Thanks Joe. I like your date better for a June 1970 car.

                Mark------

                I believe that the 3940960 water pump casting was probably produced only in batches which is why there is a considerable time lag between its casting and the build date of your car. By the time that the 3940960 casting came into use the short leg style waterpump was being used only for Corvette and some MD/HD truck applications. So, given that not too many units of this waterpump were going to be required for PRODUCTION needs, the Tonawanda foundry probably considered it more efficient to cast these in batches. In addition, this casting did not last very long as it was replaced by the GM #3992077 for 1971. As such, I expect that your waterpump will have a rather low pattern number since not many patterns would have been required for a casting that was relatively low volume and short-lived.
                In Appreciation of John Hinckley

                Comment

                • Mark E.
                  Extremely Frequent Poster
                  • April 1, 1993
                  • 4528

                  #9
                  Re: Water Pump Date Code Format

                  Joe,

                  A few years ago I contacted Bill Mock, who advertises in "Driveline" and rebuilds water pumps. He said the latest 3940960 he has seen is February 9, and believes few to none were cast after this. This means later production 1970s have a wide date gap for their 0960 pump, or used a 3992077 pump.

                  Is this consistent with your information?
                  Mark Edmondson
                  Dallas, Texas
                  Texas Chapter

                  1970 Coupe, Donnybrooke Green, Light Saddle LS5 M20 A31 C60 G81 N37 N40 UA6 U79
                  1993 Coupe, 40th Anniversary, 6-speed, PEG 1, FX3, CD, Bronze Top

                  Comment

                  • Joe L.
                    Beyond Control Poster
                    • February 1, 1988
                    • 43211

                    #10
                    Re: Water Pump Date Code Format

                    Originally posted by Mark Edmondson (22468)
                    Joe,

                    A few years ago I contacted Bill Mock, who advertises in "Driveline" and rebuilds water pumps. He said the latest 3940960 he has seen is February 9, and believes few to none were cast after this. This means later production 1970s have a wide date gap for their 0960 pump, or used a 3992077 pump.

                    Is this consistent with your information?

                    Mark------

                    Generally, yes. However, I doubt that any 1970's used the 3992077 casting. My guess is that they used the 3940960 from a batch run as I mentioned previously. I doubt that Chevrolet Tonawanda was too concerned about violating the "6 month rule".

                    What is the pattern number on your casting?
                    In Appreciation of John Hinckley

                    Comment

                    • Mark E.
                      Extremely Frequent Poster
                      • April 1, 1993
                      • 4528

                      #11
                      Re: Water Pump Date Code Format

                      The 5th edition of the JG says "1970 Corvettes as early as s/n 2077 used...3992077" and "1971 up to at least s/n 1400 used... 3940960. (p. 153)

                      So you're right- this is evidence GM mass produced in large batches with lots of inventory, and simultenously picked from their old 0960 and newer 2077 water pump stock for production.
                      Mark Edmondson
                      Dallas, Texas
                      Texas Chapter

                      1970 Coupe, Donnybrooke Green, Light Saddle LS5 M20 A31 C60 G81 N37 N40 UA6 U79
                      1993 Coupe, 40th Anniversary, 6-speed, PEG 1, FX3, CD, Bronze Top

                      Comment

                      • Mark E.
                        Extremely Frequent Poster
                        • April 1, 1993
                        • 4528

                        #12
                        Re: Water Pump Date Code Format

                        Originally posted by Joe Lucia (12484)
                        Mark------

                        What is the pattern number on your casting?
                        I pulled it and shipped it off for rebuilding. I'll post it when it returns.
                        Mark Edmondson
                        Dallas, Texas
                        Texas Chapter

                        1970 Coupe, Donnybrooke Green, Light Saddle LS5 M20 A31 C60 G81 N37 N40 UA6 U79
                        1993 Coupe, 40th Anniversary, 6-speed, PEG 1, FX3, CD, Bronze Top

                        Comment

                        • Joe L.
                          Beyond Control Poster
                          • February 1, 1988
                          • 43211

                          #13
                          Re: Water Pump Date Code Format

                          Originally posted by Mark Edmondson (22468)
                          The 5th edition of the JG says "1970 Corvettes as early as s/n 2077 used...3992077" and "1971 up to at least s/n 1400 used... 3940960. (p. 153)
                          Mark-----


                          This kind of surprises me because I don't think I've ever seen a 3992077 pump with a 1970 date (even though early 1971's should show a 1970 date).
                          In Appreciation of John Hinckley

                          Comment

                          • Mark E.
                            Extremely Frequent Poster
                            • April 1, 1993
                            • 4528

                            #14
                            Re: Water Pump Date Code Format

                            Originally posted by Joe Lucia (12484)
                            Mark-----

                            This kind of surprises me because I don't think I've ever seen a 3992077 pump with a 1970 date (even though early 1971's should show a 1970 date).
                            Don't 0960 pumps use the smaller hub and bolt pattern, while 2077 pumps use the larger pattern? If so, this means 1970 used two different types of pulleys, clutches and fans depending on which pump was installed. I don't know if I've seen this either.
                            Mark Edmondson
                            Dallas, Texas
                            Texas Chapter

                            1970 Coupe, Donnybrooke Green, Light Saddle LS5 M20 A31 C60 G81 N37 N40 UA6 U79
                            1993 Coupe, 40th Anniversary, 6-speed, PEG 1, FX3, CD, Bronze Top

                            Comment

                            • Joe L.
                              Beyond Control Poster
                              • February 1, 1988
                              • 43211

                              #15
                              Re: Water Pump Date Code Format

                              Originally posted by Mark Edmondson (22468)
                              Don't 0960 pumps use the smaller hub and bolt pattern, while 2077 pumps use the larger pattern? If so, this means 1970 used two different types of pulleys, clutches and fans depending on which pump was installed. I don't know if I've seen this either.

                              Mark------

                              Generally, yes. However, it would be possible to use a 3992077 casting and use the 65-70 bearing assembly (i.e with 5/8" pilot) and the 65-70 hub pattern or a dual pattern hub (the hub OD was the same or nearly the same for 65-70 and 71-74). So, as far as I know, the factory could have used the 3992077 casting to make up a 1965-70 pump.
                              In Appreciation of John Hinckley

                              Comment

                              Working...
                              Searching...Please wait.
                              An unexpected error was returned: 'Your submission could not be processed because you have logged in since the previous page was loaded.

                              Please push the back button and reload the previous window.'
                              An unexpected error was returned: 'Your submission could not be processed because the token has expired.

                              Please push the back button and reload the previous window.'
                              An internal error has occurred and the module cannot be displayed.
                              There are no results that meet this criteria.
                              Search Result for "|||"