Tired of replacing water pumps - NCRS Discussion Boards

Tired of replacing water pumps

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  • Timothy B.
    Very Frequent User
    • December 31, 2003
    • 438

    Tired of replacing water pumps

    My water pump on my 67 small block is starting to leak again out of the weep hole. Just like everyone else, I have been there done that so many times over the years on pre mid 70's cars. My first experience with cars was helping my dad replace water pumps I think! Now, my car is a driver and I would really like to install a water pump that I can count on lasting. I historically get about 4 or 5 years out of a water pump regardless of mileage. My question is this: Has anyone found a good replacement water pump that looks OK once installed that can be expected to last? I understand reading other posts that GM used a smaller diameter shaft up to some point and then fixed the problem by using a larger shaft. Maybe someone has made a retrofit pump with larger shaft that will still fit my fan and pulleys? The p/n of my existing pump is 3782608. Any thoughts?
  • Duke W.
    Beyond Control Poster
    • December 31, 1992
    • 15633

    #2
    Re: Tired of replacing water pumps

    Check the pulley alignment and belt tension.

    These standard SAE spec automotive water pump bearings are available in two different sizes and styles. Both 5/8" and 3/4" bearings are available in ball-ball style and ball-roller style where the front roll of balls is replaced by rollers.

    I've never had a 5/8" ball-ball type water pump bearing last more than 40-50K miles.

    Find a local rebuilder and specifically have them use the 5/8" ball-roller bearing. They are interchangeable with the 5/8" ball-ball style. This should improve mean pump life by at least 50 percent.

    Duke

    Comment

    • Joe L.
      Beyond Control Poster
      • January 31, 1988
      • 43198

      #3
      Re: Tired of replacing water pumps

      Originally posted by Timothy Bond (41147)
      My water pump on my 67 small block is starting to leak again out of the weep hole. Just like everyone else, I have been there done that so many times over the years on pre mid 70's cars. My first experience with cars was helping my dad replace water pumps I think! Now, my car is a driver and I would really like to install a water pump that I can count on lasting. I historically get about 4 or 5 years out of a water pump regardless of mileage. My question is this: Has anyone found a good replacement water pump that looks OK once installed that can be expected to last? I understand reading other posts that GM used a smaller diameter shaft up to some point and then fixed the problem by using a larger shaft. Maybe someone has made a retrofit pump with larger shaft that will still fit my fan and pulleys? The p/n of my existing pump is 3782608. Any thoughts?

      Timothy----


      If you wish to stay with a "correct" waterpump casting configuration (which your 3782608 would be for a 1967 300 hp), you can't do much more than Duke suggests. The '608' waterpump casting will not accept a "jumbo" size bearing (i.e. the size used for all 71+ applications).

      You can use an aftermarket aluminum pump like a Weiand or Edelbrock. These are designed with a "jumbo" bearing.

      It's also possible to use the 71+ small block Corvette pump castings. However, they need to be modified slightly to work for a pre-71 application and they also have to be fitted with a shaft with a 5/8" pilot and a "dual pattern" hub.
      In Appreciation of John Hinckley

      Comment

      • Mark P.
        Very Frequent User
        • May 13, 2008
        • 934

        #4
        Re: Tired of replacing water pumps

        You might want to give Bill Mock a call. He is in the Driveline. He guarantees his pumps for life and has a definate opinion on the manufacturer of bearings (i.e. FAG) and impellers he likes to use. He has a good reputation for quality work. The pump for your application would be about $150.

        Comment

        • Timothy B.
          Very Frequent User
          • December 31, 2003
          • 438

          #5
          Re: Tired of replacing water pumps

          Thanks for the replies. So, based on your experiences, if I were to get my existing pump rebuilt with quality bearings and parts, what is the life I should expect out of the pump? I drive the car about every two weeks around the area, and occasionally longer trips, about 2000 miles per year max probably.

          Also, are there any suppliers of modified 71+ pumps as Joe suggests with the larger bearings and dual pattern hubs?

          What are the desired casting numbers of the later pumps with larger bearings?

          Thanks!
          Last edited by Timothy B.; June 19, 2009, 07:57 PM.

          Comment

          • Joe L.
            Beyond Control Poster
            • January 31, 1988
            • 43198

            #6
            Re: Tired of replacing water pumps

            Originally posted by Timothy Bond (41147)
            Thanks for the replies. So, based on your experiences, if I were to get my existing pump rebuilt with quality bearings and parts, what is the life I should expect out of the pump? I drive the car about every two weeks around the area, and occasionally longer trips, about 2000 miles per year max probably.

            Also, are there any suppliers of modified 71+ pumps as Joe suggests with the larger bearings and dual pattern hubs?

            What are the desired casting numbers of the later pumps with larger bearings?

            Thanks!

            Timothy-----


            Under your usage conditions I would think that a standard 55-70 style pump would last a lifetime. I don't understand why you have the need to keep replacing them.

            I don't know of anyone that advertises making a 71+ style pump work for 55-70 Corvette applications, but some of the rebuilders like Bill Mock could probably do it.

            There are only 2 castings for the 71+ style short leg waterpump. GM #3991399 is one and GM #330813 is the other. For a 55-70 Corvette application without external bypass, the 3991399 would have a configuration most similar to the '608' casting. For 55-70 applications with external bypass, the 330813 would appear most like the originally used castings.
            In Appreciation of John Hinckley

            Comment

            • Jack H.
              Extremely Frequent Poster
              • March 31, 1990
              • 9906

              #7
              Re: Tired of replacing water pumps

              Let's see...I've logged +60K miles on the rebuilt 3991399 on my '71. And, there are folks in the chapter here who've gotten +30K miles out of their small shaft/small bearing earlier pumps.

              Our Denver local water pump rebuilder prides himself on NOT re-using factory original shafts + using top drawer pump bearings. Mayhaps, you've been the victum of less that top draw water pump rebuild cycles...

              Comment

              • Timothy B.
                Very Frequent User
                • December 31, 2003
                • 438

                #8
                Re: Tired of replacing water pumps

                Well here is a question for the forum: Which is harder on the pumps, time or mileage? My last two pumps each lasted about 4 years but with only probably 8K or less actual mileage on each pump.

                Comment

                • Joe L.
                  Beyond Control Poster
                  • January 31, 1988
                  • 43198

                  #9
                  Re: Tired of replacing water pumps

                  Originally posted by Timothy Bond (41147)
                  Well here is a question for the forum: Which is harder on the pumps, time or mileage? My last two pumps each lasted about 4 years but with only probably 8K or less actual mileage on each pump.
                  Tim-----


                  I would say that USAGE (i.e. "mileage") is the main factor in pump deterioration. However, regardless, IF the main factor were TIME-in-service, then it's not going to really matter whether you use a 55-70 style pump or a 71-74.
                  In Appreciation of John Hinckley

                  Comment

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