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BB - Replace high pressure oil pump?

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  • Joe R.
    Extremely Frequent Poster
    • May 31, 2006
    • 1822

    BB - Replace high pressure oil pump?

    Hi,

    I have my L72 (427 / 425) on an engine stand. After reading some posts on this board, I am wondering if I should replace the oil pump. During the rebuild my machinist and I agreed to put in a high volume / high pressure pump. Would I be better off with the stock version? I may get it PV judged someday.

    Thanks,
    Joe
  • Joe C.
    Expired
    • August 31, 1999
    • 4598

    #2
    Re: BB - Replace high pressure oil pump?

    You should not use a high volume pump unless you are running wide bearing clearances for racing use. With normal clearances, the flow capacity of a standard pressure/standard volume pump, or a high pressure/standard volume pump are more than adequate to supply all but the most worn-out non race applications. If your engine bearings are extremely worn, you may use a high volume pump.....
    Last edited by Joe C.; November 22, 2008, 08:19 AM.

    Comment

    • Dale S.
      Expired
      • November 12, 2007
      • 1224

      #3
      Re: BB - Replace high pressure oil pump?

      As one who just had a high volume pump removed, save yourself the trouble of doing it later. It is on easier on the stand. Dale

      Comment

      • Howard W.
        Very Frequent User
        • December 1, 1998
        • 121

        #4
        Re: BB - Replace high pressure oil pump?

        If you replace your high volume pump with a standard pump be sure to check the pump spring tension, many of the standard pump come with a high volume spring. replace it with a standard spring before you install. If you are considering PV then you must use the standard pump and spring.

        Comment

        • Joe C.
          Expired
          • August 31, 1999
          • 4598

          #5
          Re: BB - Replace high pressure oil pump?

          Originally posted by Howard Welch (31454)
          If you replace your high volume pump with a standard pump be sure to check the pump spring tension, many of the standard pump come with a high volume spring. replace it with a standard spring before you install. If you are considering PV then you must use the standard pump and spring.
          Howard,

          You're talking high PRESSURE pump. The spring tension merely sets the pump's high pressure limit!

          You are correct in stating that the spring makes ALL the diff..........in fact, the standard PRESSURE pump is nothing more than a high PRESSURE pump, with a "lighter" regulator spring.

          A high VOLUME pump, however, is a completely different animal! It has larger flow passages, and larger lobes on the gears. Because of this, it takes more crankshaft horsepower to drive than a standard VOLUME pump. Additionally, it vibrates and pulsates more than the standard VOLUME pump, and has a greater effect on a distributor's spark scatter rate.

          People sometimes confuse PRESSURE and VOLUME.
          There are three major kinds of oil pump:
          Standard PRESSURE standard VOLUME *
          High PRESSURE standard VOLUME **
          High VOLUME

          * These are OEM equipment on all non-SHP and "quasi-SHP"(L79) engines
          ** OEM equipment on true SHP engines (with solid lifters)
          Last edited by Joe C.; November 22, 2008, 03:01 PM.

          Comment

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

            #6
            Re: BB - Replace high pressure oil pump?

            All-----


            I think there's an important thing being confused here. With respect to oil pump pressure and volume considerations, there is a difference between big block and small block engines. For a small block engine, GM never used a high volume oil pump in a PRODUCTION application. Most small blocks use a standard pressure, standard volume oil pump. Most 1963-72 Corvettes with mechanical lifter engines used a high pressure, standard volume oil pump. NONE ever used a high pressure, high volume pump. I NEVER, EVER recommend a high volume oil pump for any STREET small block engine.

            For big blocks, things are different. Most big blocks with hydraulic lifter engines used a standard pressure, standard volume oil pump. These pumps use gears that are 1.15" long and with a relief spring that provides for about 30-40 PSI (engine warmed up and at cruise RPM).

            Big blocks with mechanical lifter engines, including L-88 but excluding ZL-1, used a high pressure, standard volume oil pump. The gears are 1.15" long and the relief spring provides for about 45-60 PSI (engine warmed and at cruise RPM).

            The ZL-1 used an oil pump with a high pressure, high volume oil pump. For this pump, the gears are 1.3" long and the relief spring provides for about 45-60 PSI (engine warmed and at cruise RPM).

            Unlike the small block situation, the ZL-1 oil pump works very well for most street HP big blocks. It has been used successfully by MANY for many years. I use it and recommend it. It's not really necessary for hydraulic lifter applications but it can be used without detriment. It will produce higher oil pressure than stock, though, so that might be a problem for a PV. For mechanical lifter big blocks, it will produce the same oil pressure as NEW CONDITION original pumps used for those applications so no PV problems should be caused.

            I do not recommend, though, that the ZL-1 pump be used for any big block application with "5 quart" oil systems (i.e. most Chevelle, Camaro, and passenger car). However, all 65-74 Corvettes with big block originally used a "6 quart" system.
            In Appreciation of John Hinckley

            Comment

            • Larry S.
              Expired
              • September 19, 2007
              • 204

              #7
              Re: BB - Replace high pressure oil pump?

              Joe,
              Does an L-72 (427-425HP) have solid or hydraulic lifters?
              Thanks,
              Larry

              Comment

              • Joe C.
                Expired
                • August 31, 1999
                • 4598

                #8
                Re: BB - Replace high pressure oil pump?

                Solid (mechanical) lifters (tappets).
                Same camshaft L72, L78, L71, L89.
                Last edited by Joe C.; November 22, 2008, 03:26 PM.

                Comment

                • Joe R.
                  Extremely Frequent Poster
                  • May 31, 2006
                  • 1822

                  #9
                  Re: BB - Replace high pressure oil pump?

                  Joe,

                  Do you have a part number for the ZL1 pump? That sounds like the way to go for me.

                  Thanks,
                  Joe

                  Comment

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

                    #10
                    Re: BB - Replace high pressure oil pump?

                    Originally posted by Joe Raine (45823)
                    Joe,

                    Do you have a part number for the ZL1 pump? That sounds like the way to go for me.

                    Thanks,
                    Joe
                    Joe-----


                    It's GM #3969870 and it GM lists for about 117 bucks. This pump also is supplied complete with installed pick-up screen which is tack-welded to the pump body. The screen is installed to be at the correct position for use with Corvette big block oil pans and it may not be correct for other big block oil pans.
                    In Appreciation of John Hinckley

                    Comment

                    • Joe R.
                      Extremely Frequent Poster
                      • May 31, 2006
                      • 1822

                      #11
                      Re: BB - Replace high pressure oil pump?

                      Joe,

                      Where might I be able to get a GM part number 3969870? I live in St. Louis.

                      Thanks for your help.
                      Joe

                      Comment

                      • Clem Z.
                        Expired
                        • January 1, 2006
                        • 9427

                        #12
                        Re: BB - Replace high pressure oil pump?

                        Originally posted by Joe Raine (45823)
                        Joe,

                        Where might I be able to get a GM part number 3969870? I live in St. Louis.

                        Thanks for your help.
                        Joe
                        any chevy dealer can order it and if you do not get a discount at your chevy dealer try summit as they sell them also at a discount but you will pay S&H

                        Comment

                        • Rick M.
                          Expired
                          • May 3, 2007
                          • 76

                          #13
                          Re: BB - Replace high pressure oil pump?

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


                          I think there's an important thing being confused here. With respect to oil pump pressure and volume considerations, there is a difference between big block and small block engines. For a small block engine, GM never used a high volume oil pump in a PRODUCTION application. Most small blocks use a standard pressure, standard volume oil pump. Most 1963-72 Corvettes with mechanical lifter engines used a high pressure, standard volume oil pump. NONE ever used a high pressure, high volume pump. I NEVER, EVER recommend a high volume oil pump for any STREET small block engine.

                          For big blocks, things are different. Most big blocks with hydraulic lifter engines used a standard pressure, standard volume oil pump. These pumps use gears that are 1.15" long and with a relief spring that provides for about 30-40 PSI (engine warmed up and at cruise RPM).

                          Big blocks with mechanical lifter engines, including L-88 but excluding ZL-1, used a high pressure, standard volume oil pump. The gears are 1.15" long and the relief spring provides for about 45-60 PSI (engine warmed and at cruise RPM).

                          The ZL-1 used an oil pump with a high pressure, high volume oil pump. For this pump, the gears are 1.3" long and the relief spring provides for about 45-60 PSI (engine warmed and at cruise RPM).

                          Unlike the small block situation, the ZL-1 oil pump works very well for most street HP big blocks. It has been used successfully by MANY for many years. I use it and recommend it. It's not really necessary for hydraulic lifter applications but it can be used without detriment. It will produce higher oil pressure than stock, though, so that might be a problem for a PV. For mechanical lifter big blocks, it will produce the same oil pressure as NEW CONDITION original pumps used for those applications so no PV problems should be caused.

                          I do not recommend, though, that the ZL-1 pump be used for any big block application with "5 quart" oil systems (i.e. most Chevelle, Camaro, and passenger car). However, all 65-74 Corvettes with big block originally used a "6 quart" system.
                          Great thread. Thanks Joe, I have my L71 on a stand and think I'll go with the ZL1 pump as well. Thanks for the tip.
                          Rick

                          Comment

                          • Joe R.
                            Extremely Frequent Poster
                            • May 31, 2006
                            • 1822

                            #14
                            Re: BB - Replace high pressure oil pump?

                            I talked to my machinist again about this today. I may just manage to beat him to death with oil pump questions yet. He said he put a Melling pump in it with the 427 performance spring that was called out. He will have to do some digging to come up with part numbers. He is guessing that it will have 50 - 60 PSI with the engine warmed up at cruising RPM. Does that tell you experts anything useful?

                            Joe

                            Comment

                            • Tim S.
                              Very Frequent User
                              • May 31, 1990
                              • 704

                              #15
                              Re: BB - Replace high pressure oil pump?

                              If all things are correct (bearing clearances), a small block or big block do not need any additional pressure or volume. I just completed a 427-400 hp last year and the engine builder INSISTED on a high volume pump. Guess what, too much oil pressure. 50-55lbs @ idle warm with 5w30 Mobil 1. This is a car that won't be judged so I am not going to tear back into it. If you seek my advice......stock pump!

                              tim

                              Comment

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