Low oil pressure?

Discussion in 'Small Block Mopar Engine' started by Cope, May 22, 2018.

  1. Cope

    Cope Well-Known Member

    Messages:
    1,894
    Likes Received:
    1021
    Joined:
    Oct 20, 2009
    Location:
    South Lake Tahoe
    Local Time:
    4:49 PM
    My new engine is having an oil pressure issue.

    At idle I make 25psi hot, 50PSI at 1000 rpm and 65+ above 2000 rpm.

    I've been doing some freeway testing and after 15 min at around 2,500-2,000 RPM I got off the free way and oil pressure dropped to almost zero. We're not talking hard on the breaks or down hill just sitting at the light. I put my foot in it to bump it up back to 25 so it was not idling at zero. Twice now I've seen it do this.

    HV pump running 20-50 Joe Gibbs oil.
    Factory car pan.

    Maybe 200 miles on a full build.
    Balance, blueprint the whole nine yards.

    I'm on my second oil change, I drained it at about 100 miles and cut the filter just to make sure all was well. No metal in the filter.

    11.5-1 comp ratio.
    Big lumpy cam (dont have the specs on hand)

    Any ideas, I'd hate to pull the engine again but I also dont want to ruin my new engine...

    Engine was built at a very good, high performance machine shop.
     
  2. toolmanmike

    toolmanmike FABO Staff Staff Member FABO Gold Member

    Messages:
    30,894
    Likes Received:
    12907
    Joined:
    Jan 18, 2006
    Location:
    Iowa
    View My Photos
    Local Time:
    4:49 PM
    Oops. Doesn't sound good. The first thing I would do is install a (or a different) manual gauge to make sure the reading is correct. There are many places inside a Mopar small block where oil pressure can go. Manually test the pressure and report back.
     
    • Like Like x 1
    • Agree Agree x 1
    • BigBlockMopar

      BigBlockMopar BigBlockMember

      Messages:
      1,498
      Likes Received:
      452
      Joined:
      May 1, 2011
      Location:
      Netherlands
      Local Time:
      11:49 PM
      I would guess your engine has very loose main and cambearings. Do you know the bearing-plays the engine was assembled with?
      Are you running adjustable roller rockers perhaps too? That would also be 'good' for a psi drop.

      25psi idling hot is already low in my book.
      ESPECIALLY with superthick oil and a High Volume pump.
       
      • Agree Agree x 2
      • Cope

        Cope Well-Known Member

        Messages:
        1,894
        Likes Received:
        1021
        Joined:
        Oct 20, 2009
        Location:
        South Lake Tahoe
        Local Time:
        4:49 PM
        Stamped rockers for now.

        I dont remember the clearance but it was checked. I'd have to dig out the paperwork.
         
      • toolmanmike

        toolmanmike FABO Staff Staff Member FABO Gold Member

        Messages:
        30,894
        Likes Received:
        12907
        Joined:
        Jan 18, 2006
        Location:
        Iowa
        View My Photos
        Local Time:
        4:49 PM
        Something as simple as leaving a galley plug out behind the timing cover could cause the problem. If the block was boiled and the galley plug under the rear main cap wasn't replaced could cause the issue.
         
        • Agree Agree x 1
        • BigBlockMopar

          BigBlockMopar BigBlockMember

          Messages:
          1,498
          Likes Received:
          452
          Joined:
          May 1, 2011
          Location:
          Netherlands
          Local Time:
          11:49 PM
          You might want to double check if the rockershafts (oil-exit holes to rockers) are mounted the correct way.
           
          • Agree Agree x 1
          • Cope

            Cope Well-Known Member

            Messages:
            1,894
            Likes Received:
            1021
            Joined:
            Oct 20, 2009
            Location:
            South Lake Tahoe
            Local Time:
            4:49 PM
            What's the orientation of the shafts? I can never remember....
             
          • BigBlockMopar

            BigBlockMopar BigBlockMember

            Messages:
            1,498
            Likes Received:
            452
            Joined:
            May 1, 2011
            Location:
            Netherlands
            Local Time:
            11:49 PM
            The oil holes need to point down and oriented to the valves.
            On stock rockershafts there will also be a notch on one end of the shaft, which will face to the center of the engine.
             
          • Jadaharabi

            Jadaharabi FABO Gold Member FABO Gold Member

            Messages:
            2,602
            Likes Received:
            2023
            Joined:
            Jan 8, 2016
            Location:
            Peoria, Illinois
            Local Time:
            4:49 PM
            Left an down.
             
            • Agree Agree x 1
            • Cope

              Cope Well-Known Member

              Messages:
              1,894
              Likes Received:
              1021
              Joined:
              Oct 20, 2009
              Location:
              South Lake Tahoe
              Local Time:
              4:49 PM
              So the notch faces the carb?

              I dont remember a plug under the rear main when I tore it down..

              Shit, more and more I'm thinking she gonna come back out.....
               
            • Jadaharabi

              Jadaharabi FABO Gold Member FABO Gold Member

              Messages:
              2,602
              Likes Received:
              2023
              Joined:
              Jan 8, 2016
              Location:
              Peoria, Illinois
              Local Time:
              4:49 PM
              Standing at the fender of the car looking in at the engine the notch on the shaft will be to your left and down.
              Either Fender left and down. It does not point to the carburetor.
              So on the front driver side it's down and on the passenger side it's at the rear and down.
               
              • Agree Agree x 1
              • jimjimjimmy

                jimjimjimmy lobsterman FABO Gold Member

                Messages:
                3,916
                Likes Received:
                698
                Joined:
                Nov 2, 2010
                Location:
                p. e. i.
                View My Photos
                Local Time:
                6:49 PM
                the plug under the rear main cap will not effect oil pressure it directs oil thru the filter
                 
                • Agree Agree x 3
                • Disagree Disagree x 2
                • Jadaharabi

                  Jadaharabi FABO Gold Member FABO Gold Member

                  Messages:
                  2,602
                  Likes Received:
                  2023
                  Joined:
                  Jan 8, 2016
                  Location:
                  Peoria, Illinois
                  Local Time:
                  4:49 PM
                  At the same time I also recommend that you replace the stock bolts with harder bolts. the old Originals will strip or break. Do not over torque them.
                   
                • Jadaharabi

                  Jadaharabi FABO Gold Member FABO Gold Member

                  Messages:
                  2,602
                  Likes Received:
                  2023
                  Joined:
                  Jan 8, 2016
                  Location:
                  Peoria, Illinois
                  Local Time:
                  4:49 PM
                  If that plug underneath the oil sending unit is not in there it most definitely will affect the oil pressure.
                   
                • jimjimjimmy

                  jimjimjimmy lobsterman FABO Gold Member

                  Messages:
                  3,916
                  Likes Received:
                  698
                  Joined:
                  Nov 2, 2010
                  Location:
                  p. e. i.
                  View My Photos
                  Local Time:
                  6:49 PM
                  im not talking about that plug . I am talking about the one under the rear main as mentioned .
                   
                • Cope

                  Cope Well-Known Member

                  Messages:
                  1,894
                  Likes Received:
                  1021
                  Joined:
                  Oct 20, 2009
                  Location:
                  South Lake Tahoe
                  Local Time:
                  4:49 PM
                  The strange thing is it only happens when I get off the freeway..

                  Around town is ok.
                   
                • jimjimjimmy

                  jimjimjimmy lobsterman FABO Gold Member

                  Messages:
                  3,916
                  Likes Received:
                  698
                  Joined:
                  Nov 2, 2010
                  Location:
                  p. e. i.
                  View My Photos
                  Local Time:
                  6:49 PM
                   
                • jimjimjimmy

                  jimjimjimmy lobsterman FABO Gold Member

                  Messages:
                  3,916
                  Likes Received:
                  698
                  Joined:
                  Nov 2, 2010
                  Location:
                  p. e. i.
                  View My Photos
                  Local Time:
                  6:49 PM
                  try some extra oil maybe its going low at constant rpm
                   
                  • Like Like x 1
                  • Agree Agree x 1
                  • Jadaharabi

                    Jadaharabi FABO Gold Member FABO Gold Member

                    Messages:
                    2,602
                    Likes Received:
                    2023
                    Joined:
                    Jan 8, 2016
                    Location:
                    Peoria, Illinois
                    Local Time:
                    4:49 PM

                    That is the plug under the rear main cap if you turn the motor over you'll see that's where you screw the sending unit in.

                    If that plug being out doesn't make any difference then why would Chrysler spend the time to put it in there.
                    You won't notice that plug just looking but if you stick a long bolt in there you can feel it. And if you drive it out you drive it out from the top using a long push rod.
                     
                  • toolmanmike

                    toolmanmike FABO Staff Staff Member FABO Gold Member

                    Messages:
                    30,894
                    Likes Received:
                    12907
                    Joined:
                    Jan 18, 2006
                    Location:
                    Iowa
                    View My Photos
                    Local Time:
                    4:49 PM
                    Here!

                    Oil galley plug enlarged.jpg
                     
                    • Agree Agree x 1
                    • jimjimjimmy

                      jimjimjimmy lobsterman FABO Gold Member

                      Messages:
                      3,916
                      Likes Received:
                      698
                      Joined:
                      Nov 2, 2010
                      Location:
                      p. e. i.
                      View My Photos
                      Local Time:
                      6:49 PM
                      it directs oil thru the filter . without this plug the oil will bypass the filter .
                       
                      • Agree Agree x 4
                      • Cope

                        Cope Well-Known Member

                        Messages:
                        1,894
                        Likes Received:
                        1021
                        Joined:
                        Oct 20, 2009
                        Location:
                        South Lake Tahoe
                        Local Time:
                        4:49 PM
                        Oh boy....

                        I dont think I ever drove that one out....

                        That passage could have been full of glass beads.....
                         
                      • Jadaharabi

                        Jadaharabi FABO Gold Member FABO Gold Member

                        Messages:
                        2,602
                        Likes Received:
                        2023
                        Joined:
                        Jan 8, 2016
                        Location:
                        Peoria, Illinois
                        Local Time:
                        4:49 PM
                        That plug is sitting approximately 7 and a quarter inch down inside that hole. You can check to see if it's in there by taking off the oil pressure sending unit and inserting a rod and measuring how far it goes down.



                        If it goes over 7 and 1/2 in then it is missing.
                         
                      • inertia

                        inertia Well-Known Member

                        Messages:
                        2,985
                        Likes Received:
                        353
                        Joined:
                        Feb 4, 2011
                        Location:
                        Victoria B.C. Canada
                        View My Photos
                        Local Time:
                        2:49 PM
                        You're both talking about the same plug. I've fought this battle before, good luck.
                         
                        • Agree Agree x 1
                        • Jadaharabi

                          Jadaharabi FABO Gold Member FABO Gold Member

                          Messages:
                          2,602
                          Likes Received:
                          2023
                          Joined:
                          Jan 8, 2016
                          Location:
                          Peoria, Illinois
                          Local Time:
                          4:49 PM
                          the oil will still go through the filter but at the back of the block without that plug it can loop back to the filter.