Oil pressure concerns

Small Block Mopar Engine

  1. 1973dust

    1973dust FABO Gold Member FABO Gold Member

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    1974 318. 40000 on factory bottom end. Running Lucas 10w30 with Wix filter. 4 extra holes drilled in oil filter mounting plate. Oil pressure is 65-70 cold and 50-55 cruising at 2300 warm as per aftermarket gauge. The two concerns I have is that pressure at 800 rpm idle with 190 coolant temp is only 20 psi. In gear drops to15-18. Pressure comes right up as soon as you touch the gas. The other thing is that on a cold start, the gauge takes 2-3 seconds to move. Acts much like first start after an oil change when filter isn't saturated yet. I ran about 1000 miles last summer using 10w30 synthetic and I'm concerned it may have super-cleaned the inside of the engine and sludged up the oil pickup. Maybe I'm just paranoid. I do have another mech gauge that I could hook up temporarily to see if it shows same as Autogage. Thanks for any opinions.
     
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    • 318willrun

      318willrun Utube channel 318willrun

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      Especially with 10-30, idling at 20 psi with a hot engine that is still factory built is fine. 15 to 18 psi in gear idling lower with a warm engine is also fine.
       
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      • sireland67

        sireland67 FABO Gold Member FABO Gold Member

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        10 psi per 1000 rpm is factory.

        You are fine.
         
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        • 1973dust

          1973dust FABO Gold Member FABO Gold Member

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          Thanks for the fast response, guys. Do you think i should move up to 10-40 on next change?
           
        • 318willrun

          318willrun Utube channel 318willrun

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          unless you are working it hard in the desert, no need
           
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          • nm9stheham

            nm9stheham Well-Known Member

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            As above, pressures sound good hot with 10W30.

            Synthetic is not going to particularly clean out the engine. High detergent oils will. So a Rotella-like oil, with high detergency, would clean it up. But your pressures don't sound like you pickup is blocked; you would expect to see low/erratic pressures at cruise if that was the case.

            As for the 2-3 second delay in pressure build, the anti-drainback valve in the correct oil filter should help that for shorter stops, but 2-3 seconds when cold is not abnormal.
             
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            • 1973dust

              1973dust FABO Gold Member FABO Gold Member

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              Thanks again to all. I'm a master at inventing problems where they don't exist.
               
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              • PRH

                PRH Well-Known Member

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                Personally, I wouldn’t be using oils that are formulated for the current API specs.
                Use some brand of “muscle car” oil that still has the correct additive package for a 1974 vintage engine.
                 
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                • 1973dust

                  1973dust FABO Gold Member FABO Gold Member

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                  I'm currently running Lucas "Hot Rod and Classic" oil.
                   
                • S'cuder

                  S'cuder FABO Gold Member FABO Gold Member

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                  That's overkill, especially if your valvetrain is stock. At over 2000 ppm, that Lucas product has twice the ZDDP you need, and that level has shown to cause pitting and spalling.
                  Try something with around 1000 to 1200 ppm of ZDDP. There are several out there, including Valvoline VR-1, Penn Grade/Brad Penn, Driven, some Amsoil, etc. Also many diesel engine oils are good options.
                   
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                  • cudamark

                    cudamark FABO Gold Member FABO Gold Member

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                    Your pickup screen sounds ok. The symptoms of a partially plugged one is the oil pressure will go down as the RPM goes up.
                     
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                    • 66 Valiant wagon

                      66 Valiant wagon Well-Known Member

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                      This isn't an A body but I have a 1999 Jeep TJ with a hydraulic flat tappet 4 cylinder. I've had it since it had 28,000 miles and it now has 210,000. I've always just run a synthetic blend and have never added any extra ZDDP. I'm commenting because I am convinced that once the cam is broken in there isn't any need for extra additives. I know alot of my fellow Jeepers out there are convinced they do need the extra ZDDP but I guess my engine is proof they don't.
                      I don't add any my older engines either and I don't have any problems.
                      Just my $0.02
                       
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                      • nm9stheham

                        nm9stheham Well-Known Member

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                        The need for ZDDP varies with pressure lifter-to-lobe; this has been discussed in the research articles. Low pressure stock springs and mild ramp rate stock cams seem to mostly survive OK with the lower levels of ZDDP in the 800-900 ppm range that the newer oils have.

                        But you can't extend this situation to all engines and certainly not to any high performance cam and lifters.
                         
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                        • S'cuder

                          S'cuder FABO Gold Member FABO Gold Member

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                          For a stock 318, you're probably right. In 1999, when your Jeep was built, ILSAC GF2 was already in effect, which reduced the amount of Phosphorous to 1000 ppm, I think. Chrysler was is part of ILSAC, which came up with this reduction in order to preserve catalytic converter health, which were federally mandated to be warranted much longer than the rest of the vehicle.
                           
                        • S'cuder

                          S'cuder FABO Gold Member FABO Gold Member

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                          Agreed, with all except the content of ZDDP in modern oils. The new GF-6 spec mandates phosphorus between 600 and 800 ppm. This is the same as the recently current GF-5. Analysis has shown many current oils to be at the lower end of this range. Still probably fine without high psi valve springs. Also, modern oils have introduced other anti-wear additives such as molybdenum and boron. Sides are split as to how well they work in high perf cam and lifter applications. Good old ZDDP is still the go-to in those instances.
                           
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