1. Marco

    Marco Member

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    Hi everybody,

    For some reason my 400 (rebuild about 2 years ago) has basicly always around 20psi of oil pressure, it does not matter if the car is hot or cold, high rpm or at idle. It seems to max out at around 22-23 when could and cruise speed and the lowest is at hot idle its around 18-19. I've tried 3 different oil pressure sensors and gauges already so i dont think that's the problem.

    Anybody know what would cause this?

    Gr marco
     
  2. dadsbee

    dadsbee FBBO Gold Member FBBO Gold Member

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    440 in my Superbird rarely hits 10psi, been that way for over 30 years. Has lots of oil flow and doesn't knock, all that matters.

    If you want to see if you can increase the pressure, shim the oil pump bypass spring with a washer or two.
     
  3. pnora

    pnora Well-Known Member

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    Check it with a mechanical gauge.
     
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    • Master Gunner

      Master Gunner FBBO Gold Member FBBO Gold Member

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      How much bearing clearance do you have? Did you use full grooved mains? Even the stock pump "should" get better pressure than that, you could try a hemi relief spring.

      Mark
       
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      • 70chall440

        70chall440 FBBO Gold Member FBBO Gold Member

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        Is this 20 psi on the factory gauge? If so I'd say your sending unit needs to be replaced. I don't know about anyone else but 20 psi at any time would get my attention. My 440 in my 70 challenger runs like 70-90 cold and around 40-60 or so hot
         
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        • threewood

          threewood FBBO Gold Member FBBO Gold Member

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          Weird that is stays at 20psi with higher rpms as well as idle rpms. Mine idles around 14psi but jumps to 55psi when I'm driving.
           
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          • Slap Stick

            Slap Stick Well-Known Member

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            He has already used multiple gauges and senders.
             
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            • 70chall440

              70chall440 FBBO Gold Member FBBO Gold Member

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              So long as you have flow and it isn't knocking you are good, but 20 psi (or less) would have me checking it with a mechanical gauge just to be sure.
               
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              • turbine68rt

                turbine68rt FBBO Gold Member FBBO Gold Member

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                Have you confirmed pressure with a mechanical gauge?
                 
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                • BLK 68 R/T

                  BLK 68 R/T FBBO Gold Member FBBO Gold Member

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                  Only a handful of things come to mind for low oil pressure.
                  Issue with pump
                  Excessive bearing clearance
                  Missing oil galley plug
                  Lifter bore wear
                  Missing rocker shaft plug
                   
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                  • Marco

                    Marco Member

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                    Hi everybody,

                    Thanks for all the quick responses!

                    Ah that's good to hear but just for my own peace of mind I would like to be around 30-40.

                    I also tried it with an mechanical gauges but its still the same....

                    I can't really recall the clearance numbers, I'll ask te rebuilder. But when the clearances are to big shouldn't the oil pressure at idle be lower?

                    I indeed also tried new sending units and gauges.

                    Thanks again for all the responses.
                    I'm going to shim the spring tomorrow, when removing the spring will the oil start running out? I've never done this before hahaha

                    Gr Marco
                     
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                    • khryslerkid

                      khryslerkid FBBO Gold Member FBBO Gold Member

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                      Try a heavier weight oil if you haven't. I was using 20w 50w and it was almost too much pressure. Went to a 10w 30w and now it's just right. It does make a difference depending on bearing clearance.
                       
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                      • threewood

                        threewood FBBO Gold Member FBBO Gold Member

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                        Not much oil came out of mine when I pulled the plug and spring. Put a rag under it though.
                         
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                        • 91r/t

                          91r/t FBBO Gold Member FBBO Gold Member

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                          It is hard too because with large clearances they want 20w50 in it, but then my lifters wants maximum 10w30 in them so I run 10w40.......It's a never ending battle of old school vs new school parts. I haven't had any issues with 10w40, but the lifters specifically call out a lighter oil and I won't be using 20w50 for that reason which nets a lower pressure in the 20's at idle and 45 max driving.
                           
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                          • pnora

                            pnora Well-Known Member

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                            It is possible that you are losing oil pressure internally. As you said you have verified oil pressure on a known good mechanical gauge. One simple check is the rocker shaft end plugs. Make sure they are intact and not leaking. Usually if the pressure is leaking on the lifter galleys the lifters will be noisy. I suppose there could be something with the oil pump. At least it is easy to change.
                             
                          • 747mopar

                            747mopar FBBO Gold Member FBBO Gold Member

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                            If it's clearance issues you might switch to a HV oil pump. Any PSI reading at all shows your delivering more oil than the motor is using (restricted flow = pressure) so 20psi isn't necessarily something to worry about. IMO people with super high oil pressure are just wasting unnecessary hp driving the pump.

                            What I find odd is the 18-23, that's very odd for it to be almost identical from idle to cruise? That makes me lean more towards the pressure bypass, sounds like it's just won't build pressure beyond 23? I'd definitely start with the bypass spring or even throw another pump on it... us Mopar guys have it easy on that one:thumbsup:

                            I find it hard to believe that you could have an internal leak/clearance issue that causes pressure problems at cruising rpm yet it's right where it should be at idle.. :screwy:
                             
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                            • Moparnocar

                              Moparnocar Well-Known Member

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                              They make an adjustable relief spring too, I've got a new one I'd sell for a little less than new, even tho it's new
                               
                            • 69Bee

                              69Bee FBBO Gold Member FBBO Gold Member

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                              Missing pipe plugs on the front (2) would give very low to no oil pressure. Here are a few other ideas:
                              1) Wrong lifters-uncovered lifter oil groove bleeding off oil
                              2) Hollow push rods allowing 16 oil bleeds to the heads
                              3) Rocker shafts on backwards so rocker oil holes are not at the bottom of the rocker, possible excessive oil bleed (Dr. side notch front & down, Pass side notch rear & down)
                              4) Oil pressure relief valve stuck open in full by-pass mode
                               
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                              • Kern Dog

                                Kern Dog FBBO Gold Member FBBO Gold Member

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                                FRAM oil filter?
                                As simple as it seems, these filters have caused problems for people.
                                 
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                                • 451Mopar

                                  451Mopar Well-Known Member

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                                  Pull the pressure regulator out of the pump and make sure nothing is keeping it from sealing. Check that the spring is not broken or a wrong spring in the pressure relief.
                                  If you think there is excessive leakage, you could shim the pressure spring to try to make the pump output maximum volume/pressure (as a test.)
                                  The pump might also be sucking air into the input. There should be a "O" ring on the pump where it goes into the block to prevent this.
                                   
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