rpm's up = oil pressure drop? ;-(

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by srt1955, Mar 20, 2015.

  1. srt1955

    srt1955 New Member

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    I am running a 500ci Brad block ,with an RCD dry sump pump with a BDS 8-71, in a older nostalgia funny car.
    My problem is that when I rev the engine, the oil pressure will drop. It can start out at 160, at idle, but when I start to bring the rpm's up, the pressure starts falling all the way down to around 80 psi.
    When the engine returns to idle so does the oil pressure.
    I am running 60 weight oil, I have pulled the pump apart, but cannot find any issues,etc. Also I am running a system 1 oil filter.
    To rule out the dry sump tank , I have even went as far as running the engine with the pressure and return hoses in a 5 gallon bucket of oil.
    By observing this, I was surprised as I thought the oil level in the bucket would start to fall when reviving the engine, But the level remains virtually the same as when at idle.... Any ideas.. thanks..srt1955.
     
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  2. Nitro Madness

    Nitro Madness Super Comp

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    Just a thought - System One makes several filter inserts with different screen densities for thin or thick oil weights - make sure you have the correct insert for 60 wt. oil.
     
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  3. srt1955

    srt1955 New Member

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    Not sure of the screen density, but I did do a test fire with out the element in the filter, but nothing changed.
     
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  4. Nitro Madness

    Nitro Madness Super Comp

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    That rules out the filter insert.....
     
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  5. blownapex

    blownapex Member

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    oil pressure

    make sure the inlet and outlet at the filter are correct
     
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  6. Randy G.

    Randy G. Top Alcohol

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    Read this thread. You may find your answer.

    http://www.insidetopalcohol.com/sho...r-oil-pump-flow-meter-and-pressure-comparison
     
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  7. Mark Leigh

    Mark Leigh Member

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    Has this engine combo ever had good oil pressure before or is it a new setup that has a problem ?

    Also is the block setup for priority oiling ?
     
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  8. jay70cuda

    jay70cuda Member

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    Put several gauges on it. When I had problems I had a gauge on pump Inlet back of cam and one up where my rocker oil feeder line went for rocker gear. If your main clearance is excessive it will drop psi. Also make sure all the cam oil plugs are in and you put orings on them. That will cause exact same problem. Been there done that one.
     
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  9. srt1955

    srt1955 New Member

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    Yes, has had good oil pressure, pump is used, but has never gave any issues until now.
    What is priority oiling? ( I am reading pressure off of the front of the pump / outlet side.)
     
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  10. Mark Leigh

    Mark Leigh Member

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    Priority oiling is a second oil galley in the back of the block on the left side of the cam as looking at from the drivers seat -- the galley can feed one or 4 main bearings with additional oil ----

    to lose that much press when idling it may have a sticky bypass valve -- Have you hurt a piston and had a little trash circulating ?

    When I install those red plugs in the galleys I use grease to fill the snap ring groove to help keep the o ring from tearing while tapping it in with a slide hammer -----

    -is your suction line from the pan tightly clamped and your fittings in good order on the flare ? You could have a suction loss somewhere ---
     
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    Last edited: Mar 24, 2015
  11. Blown5402

    Blown5402 Member

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    Pan to oil pump suction line

    I had the same problem one weekend showing close to the same problem. My oil line was not the proper line or stiffness and would suck together when I reved the motor or did a burnout, nearly no oil pressure. I would get back to the pits, start the motor and great oil pressure. I got home and felt of the oil line and could squeeze it flat. Changed the line and never any oil issues again! I hope this might help! Jim in TN
     
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  12. Mark Leigh

    Mark Leigh Member

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    Agree with above post, you should not be using braided hose between the pan and pump -- should be hydraulic suction hose with the red , green or yellow stripe --
     
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  13. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    Ptfe

    I have used both smooth bore and fully convoluted PTFE style hose with success. I know our Goodridge smoothbore hose is rated to 50 lbs of vacuum. It's a lighter and cleaner looking set up than the reinforced hydraulic line with the slip on fittings and clamps.

    Conventional rubber style hoses should not be used on the suction side of the oiling system.

    Also some of the cheaper style fittings will suck air past an o-ring if you have a swivel fitting.
     
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  14. srt1955

    srt1955 New Member

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    thanks everyone for the suggestions.
    I have since changed the oil hose from dry sump to pump and tried different hoses from the suction side of the pan to pump.
    Also tried a different drysump tank. Tried reading the pressure from the back of the block, different gauges, also checked all main and rod bearings ... Still the same thing. 180psi at idle. After about 30 seconds I start to rev the engine and the psi drops as low as 70 psi, let it come back to idle and it will be around 170psi... Rev. the engine and the same pressure drop.
    It really acts like it cannot pull enough oil when rpms go up. Like I said I cannot see the level drop in the dry sump or even the bucket, when rpms go up. It just remains the same level either at idle or 6000 rpm. I have even tried another pump... I'm really stumped.............??
     
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  15. Mark Leigh

    Mark Leigh Member

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    What does the oil pan suction fitting look like ? What size screen ?
     
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  16. Mark Leigh

    Mark Leigh Member

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    Have you confirmed that the plus and o rings in the front of the block are installed correctly as Jay mentioned ?
     
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  17. srt1955

    srt1955 New Member

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    I haven't had the oil galley plugs out sine late 2013. I guess an Oring maybe could have went bad, ?
    Do you all think the oil is just to thick for the pump to pull it, until it is really warmed up. ?
    As now it seems to be aerated when looking at it in the tank. As in the pump is cavitating.
     
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  18. Mark Leigh

    Mark Leigh Member

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    What was the ambient temp when you tried firing the engine ?
     
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  19. Mark Leigh

    Mark Leigh Member

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    Is the pan dry when you fire up the engine ? Have you ever tried putting 2 qts in the pan before fire up ?
     
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  20. srt1955

    srt1955 New Member

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    Found the problem!
    Evidently the oil was just to thick to be pulled thru the pump. Temp of the oil and engine when cranked were about 68 degrees.
    For trial purposes we put 10w-30 in the oil tank. Fired the engine up , idled for about 1 minute, brought the rpms up and in turn the oil pressure increased with rpm's..... Yeah!
    So we will be putting a oil heater in the dry sump tank.
    Thanks everyone for all of the input...... like 99% of the time, the answer is to most problems is not that complicated..........
     
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