1972 LT-1 water pump - NCRS Discussion Boards

1972 LT-1 water pump

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  • Martin Z.
    Infrequent User
    • January 1, 1998
    • 26

    1972 LT-1 water pump

    I need help in determining what is the correct water pump for my 72 LT-1 with factory air. I believe that the judging manual may be incorrect. I have located a water pump GM # 330813 as indicated in the judging manual. However, it states that the pump has a boss for a by-pass port, but they are not drilled for the port. Every pump I have seen for this application seems to have the boss drilled. Please advise as I need to replace my water pump due to leaks. Thanks very much

    Marty
  • Joe L.
    Beyond Control Poster
    • February 1, 1988
    • 43193

    #2
    Re: 1972 LT-1 water pump

    Marty-----

    I've seen a few of these non-tapped 330813 castings but VERY FEW. They are quite rare. I believe that they were a PRODUCTION item only, were DEFINITELY used on Corvettes only (the 330813 casting was used ONLY for Corvettes and some MD/HD trucks), and were used for only a very short period of time during the 1972 model year. Hence, their rarity.

    For 1972, I believe that 3 different waterpump castings were used for small blocks. Early 1972, through about March, 1972, used the GM #3991399 casting as used for the 1971 model year. This casting has no provisions for external bypass, at all. The upper portion of the casting is very similar to the 3782608 which was widely used during the pre-71 period. I believe that for a short time, most likely about April-May 1972, the 330813 pumps without tapped upper bosses MAY have been used. After about that time, I believe the 330813 pumps WITH the tapped and plugged bosses were used and this then continued through the end of the 1972 model year and, in fact, right through the end of the 1982 model year.

    Unless your car was built during about the April-May, 1972 period, I don't think that it would have used the untapped 330813 pump.

    In any event, if you wish an untapped 330813 pump you will likely have a difficult time finding one. Bill Mock might be able to help, but I sort of doubt it on this one.

    However, you can still have one. Here's how: obtain a pump with a drilled and tapped 330813 casting which are not too difficult to find. Install an internal hex head pipe plug into the drilled and tapped boss so that the top of the plug is below the top of the boss. You may have to grind the TOP of the pipe plug a little to achieve this fit. Next, apply JB Weld to the area on top of the pipe plug so that it "mounds up" a bit and covers the entire top area of the boss. After it cures, grind it smooth so that it follows the contour of the boss, but don't grind it down so much that all the JB Weld is removed from the area of boss surrounding the hole or you'll get a "shadow" of the hole. Presto! You've restored the original configuration of the untapped 330813 pumps. After the pump is painted Chevrolet orange, NO ONE will know the difference.

    If your car was not built during the April-May, 1972 period, I wouldn't even go to this trouble. Actually, I believe that if any of these untapped 330813 castings were used on Corvettes, they were used for a MAXIMUM of the April-May, 1972 period. It may actually only have been for as little as a week or two sometime during this period rather than the entire April-May period.
    In Appreciation of John Hinckley

    Comment

    • Martin Z.
      Infrequent User
      • January 1, 1998
      • 26

      #3
      Re: 1972 LT-1 water pump

      Joe: Thanks so very much for the help on my water pump issue. My car was built in June so I should be OK with the tapped 330813 casting. I got a rebuild from Dr. Rebuild. Thanks again for the speedy response!

      Marty

      Comment

      • Patrick H.
        Beyond Control Poster
        • December 1, 1989
        • 11608

        #4
        Re: 1972 LT-1 water pump

        Hmmmm.

        I'd love to see if any cars with their original pumps actually have the drilled and tapped top.

        My 72 does have it drilled and tapped, but it is one of the VERY few parts replaced on the car, so I can't help. It's a June 72 car.

        Patrick
        Vice-Chairman (West), Michigan Chapter NCRS
        71 "deer modified" coupe
        72 5-Star Bowtie / Duntov coupe. https://www.flickr.com/photos/124695...57649252735124
        2008 coupe
        Available stickers: Engine suffix code, exhaust tips & mufflers, shocks, AIR diverter valve broadcast code.

        Comment

        • Joe L.
          Beyond Control Poster
          • February 1, 1988
          • 43193

          #5
          Re: 1972 LT-1 water pump

          Patrick-----

          I've seen so few of these untapped 330813 castings that it's hard to believe that they could have been used for approximately half of the 1972 Corvette model year.
          In Appreciation of John Hinckley

          Comment

          • Patrick H.
            Beyond Control Poster
            • December 1, 1989
            • 11608

            #6
            Re: 1972 LT-1 water pump

            I agree.

            Tom has an LT-1 AC car built almost the same time as my own 72. I think I'll have to check that car out, and see what water pump is on it. That may help figure it out.

            Patrick
            Vice-Chairman (West), Michigan Chapter NCRS
            71 "deer modified" coupe
            72 5-Star Bowtie / Duntov coupe. https://www.flickr.com/photos/124695...57649252735124
            2008 coupe
            Available stickers: Engine suffix code, exhaust tips & mufflers, shocks, AIR diverter valve broadcast code.

            Comment

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