High oil pressure

1971 - 1974 Mopars

  1. pjm8047

    pjm8047 Well-Known Member

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    on my 71 rr 383 the oil pressure gauge reads somewhere between 3/4 and high depending on rpms. It’s been like that for years. It seems to be running ok. Running 10w30 with stp oil treatment. 36k on motor never rebuilt all original. Is that normal?
     
    Last edited: Jun 12, 2019 at 9:15 AM
  2. Darter6

    Darter6 FBBO Gold Member FBBO Gold Member

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    Sounds like a healthy engine to me.If it bothers you hook a manual gauge to it and see what the numbers really are.
     
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    • pjm8047

      pjm8047 Well-Known Member

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      Ok cool Thanks. Just was wondering owners manual doesn’t say. Just had oil pan gasket and fuel pump gasket replaced. No more leaks! Fyi if anyone needs to replace there oil pan gasket on your big block the Fel-Pro 1808 is a way to go .
       
    • pjm8047

      pjm8047 Well-Known Member

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      I trust you. I just wish they designed of those gauges little bit better more the a L and H. It runs closer to H at 2,500 rpm.
       
    • 68Moparmaniac

      68Moparmaniac Well-Known Member

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      Better than the alternative ….
       
    • pjm8047

      pjm8047 Well-Known Member

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      True lol
       
    • Darter6

      Darter6 FBBO Gold Member FBBO Gold Member

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      Tell ya a little story, Back in 1974 I spun a rod bearing in my 340 Duster. I got a brand new factory 318 to replace it as I was off to school 1600 miles from home and thought I needed a reliable car instead of a fast one. Anyway what I'm getting at , I installed a Sun oil pressure gauge when the 340 was in there,well the 318 had much higher oil pressure than the 340 ever had. Cold (Denver winter) the gauge would read over 100 psi and hot running at road speed 60-80 psi. I too thought there may be something wrong but I did nothing thinking "Oh well". That car went on to 2 more owners before owner #3 wrapped it around a tree.
      Also, Factory gauges leave much to be desired. I have more faith in a oil light.
       
    • Fran Blacker

      Fran Blacker FBBO Gold Member FBBO Gold Member

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      Why run STP that will increase oil pressure, MO.
       
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      • pjm8047

        pjm8047 Well-Known Member

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        For the zinc zddp
         
      • Fran Blacker

        Fran Blacker FBBO Gold Member FBBO Gold Member

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        Ok. If your concerned about oil pressure, isn't another product that won't increase OPressure. Stuff not as cheap as STP? One example.
        https://www.summitracing.com/parts/cca-159
         
      • pjm8047

        pjm8047 Well-Known Member

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        I was just a question. I read alot of good reviews on the stp. Might switch to lucas zinc additive next year.
         
      • Fran Blacker

        Fran Blacker FBBO Gold Member FBBO Gold Member

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        Friend worked at Secord Chrysler/Plymouth in 1968 to 70. Some early SixPack cars were popping lifters apart. To much oil pressure, they'd bury a 100 lbs gauge. They replaced the pumps.
         
      • RJRENTON

        RJRENTON Well-Known Member

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        Gentlemen,
        For what it's worth....my GTX...the engine is 0.030" over with 11.0:1 TRW forged pistons @ 0.003" - 0.004" clearance with moly filled rings. Full groove mains @ 0.002"-0.0025" clearance (Clevite tri metal bearings); same clearance for rod bearings. I use a Mopar high VOLUME pump with 10W-30 Mobil one with a pint of ZDDP additive. Cold oil pressure is 80 psi, hot oil pressure @ 3000 RPM is 75 PSI; Hot oil pressure at 1200 RPM idle is 50-55 PSI. Too much pressure???? I do not think so. Because of the full gtoove mains, to guard against a spun bearing, I torque the main cap bolts (ARP) 15-18 LB/ft more than the FSM specs. I also use ARP hardware on the rods. I have no problems with the lifters (Crane also plus Crane roller rocker arms).
        I'm sure others will disagree (or not) as they have their own recepie for engine building. This is what works for me.
        Bob Renton
         
      • 68Moparmaniac

        68Moparmaniac Well-Known Member

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        If your motor was built with a high pressure pump instead of a high volume pump this could be the reason for the high pressure issue. If you don't want to replace your pump you can access the oil pump pressure regulator spring and replace it with a lower spring rate. 1se839.jpg
         
        Last edited: Jun 13, 2019 at 6:27 AM
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        • RJRENTON

          RJRENTON Well-Known Member

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          68Moparmaniac,
          System oil pressure is a function of:
          1) Bearing clearances (both mains & rods)
          2) Oil viscosity (higher viscosity = higher pressures)
          3) Valve lifter to bore clearance
          4) is the pump a HIGH VOLUME or HIGH PRESSURE
          Most people attribute high pressure to the pump's relief valve spring's tension. Stiffer spring = higher pressures. True to some extent, however bearing clearance is usually the biggest influence on pressure. The greater the clearance the LOWER the pressure at a given RPM. The pump can't supply enough VOLUME because of excessive clearances so the result is a lower pressure. If this is the case, increasing the pump's relief valve spring's tension will have no effect. Increasing the oil's visvodity MAY increase the pressure slightly. The only real way is to increase the pump's VOLUME capabilities is to replace it OR decrease the volume requirements by DECREASING the bearing clearances. Boyle's Law proves this by the volume / pressure relationship. Pressure is INVERSELY PROPORTIONAL to the Volume required. Since the pump is a fixed displacment device, if higher volumes required, lower pressures will result. The fix: use a high VOLUME pump, decrease bearing clearances, increase oil viscosity or some combination of all. This is just my opinion, I'm sure others will disagree.
          Bob Renton
           
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