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Thread: Oil pressure

  1. #1
    Senior Member MASTER BUILDER
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    Oil pressure

    I was at the dyno on friday and started the motor up for first time 60 psi oil pressure........u did some pulls on the motor and the oil pressure dropped slowly by 8 to 10 psi......as the motor warmed up more had same rsults.........my clearnaces are fine on the crank and the rods. At first thought maybe to much oil so we drained some and with same results, so we added some and same results..........ok for the rest of the story........pulled off the oil filter and cut it open and found foam in the oil......we ran quite a few pulls on the motor and did 4 filter changes on the motor...foam was present in all filters.......we changed the oil twice and the oil had some foam in it............the pump has to be cavitying, have you ever seen a oil pump have a crack in it........i pulled the pan off tonight and measured the clearnace between the pan and the pump it was fine............so next i will pull the pump out and check the screen and pull off the pump and look at it.........is there anything else for ideas to check you guys can think of..........also i don't have a gasket between the pump and the block, do u recommend one or not............i don't think i am running out of oil it is 7 quarts oil pan not sure of the oil pump brand suppose to be high output..............thanks for any input

  2. #2
    Senior Member RACING JUNKIE
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    Re: Oil pressure

    Quote Originally Posted by fishman1
    not sure of the oil pump brand suppose to be high output
    Oh my...

    How about you throw it away and buy a good pump before you have to buy another crank and set of rods, and maybe a block, pushrods, rockers, the list goes on!
    -WJ Birmingham

    OneBadGMC.com

  3. #3
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    Re: Oil pressure

    Quote Originally Posted by OneBadGMC
    Quote Originally Posted by fishman1
    not sure of the oil pump brand suppose to be high output
    Oh my...

    How about you throw it away and buy a good pump before you have to buy another crank and set of rods, and maybe a block, pushrods, rockers, the list goes on!
    I already ordered a new pump i was checking if anybody had any other ideas on the problem

  4. #4
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    I would make sure that the pick-up tube doesn't have a crack in it and that it is sealing good inside the pump. I weld the pick-up into the pump, but have seen the tube have a crack before. Also, no gasket between the pump and the main cap, but do make sure that the cap has a good sealing surface and doesn't have divots or cracks causing leaks. I use an ARP oil pump stud and nut, but make sure that it doesn't thread down too far into the main bearing.

    You might also want to make sure that the oil is draining back down into the pan OK. Because that is a way to go through the 7 quarts, if it is staying at the top and not draining quickly out of the heads and past the lifter screens.

    I don't think that you ever mentioned what weight of oil that you are running.

    Bill M

  5. #5
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    Quote Originally Posted by sp2816
    I would make sure that the pick-up tube doesn't have a crack in it and that it is sealing good inside the pump. I weld the pick-up into the pump, but have seen the tube have a crack before. Also, no gasket between the pump and the main cap, but do make sure that the cap has a good sealing surface and doesn't have divots or cracks causing leaks. I use an ARP oil pump stud and nut, but make sure that it doesn't thread down too far into the main bearing.

    You might also want to make sure that the oil is draining back down into the pan OK. Because that is a way to go through the 7 quarts, if it is staying at the top and not draining quickly out of the heads and past the lifter screens.

    I don't think that you ever mentioned what weight of oil that you are running.

    Bill M
    I am running 20-50 oil and the block is a dart little m shouldn't be a problem with oil coming back fast enough

  6. #6
    Administrator RACING JUNKIE bjuice's Avatar
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    are you saying the oil pressure will start showing a drop in pressure as you are turning up the rpm's or when you are off the throttle and rpm's are backing down. ?
    after motor was warm what was your final full throttle oil pressure?

    last question, what type of oil pump is in motor now ?
    Bjuice..

    "I'M YOUR HUCKLEBERRY ! "

  7. #7
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    Quote Originally Posted by bjuice
    are you saying the oil pressure will start showing a drop in pressure as you are turning up the rpm's or when you are off the throttle and rpm's are backing down. ?
    after motor was warm what was your final full throttle oil pressure?

    last question, what type of oil pump is in motor now ?
    Bjuice

    the oil pressure starts to drop very slowly as the rpms go up....starts at 60 psi oil pressure and dropped to 52 psi, warmed up the motor further after more dyno pulls and oil pressure started at 50 psi and dropped to around 40 psi.

    The oil pump brand i am not sure as it was fairly new and i just used it off my last motor which only had 130 passes on it and i didn;t build that motor......i have a melling hv55 pump coming..........do you weld your pickup tube in or just press it in..curious how everybody does it

    thanks

  8. #8
    Administrator RACING JUNKIE bjuice's Avatar
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    my 400ci did the exact thing 5 or so years ago..it was a melling pump also...i replaced it with a moroso and never had any more problems but i have seen mellings run with no problems ( anything can malfunction)..i guess this is the reason for oil gauges...lol
    with the moroso i purchased the pick up tube had a bracket welded off the pick up tube to the pump housing and had a 1/4 bolt that held the pick up tube in the pump...there is pic of this pump i 'm speaking of in JEGS book ..page 56


    i did assume you were speaking of the pressure dropping as the rpm's increased but had to ask anyhow
    Bjuice..

    "I'M YOUR HUCKLEBERRY ! "

  9. #9
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    You need the melling 10550 oil pump, they are around $50.00
    We see them hold the best oil pressure on the dyno.
    This pump will hold your pressure right around 60-65 psi from 3000-8000 rpm depending on your exact bearing clearances.
    Competition Engines & Hardcore Engine Parts
    www.cnc-motorsports.com
    [email protected]

  10. #10
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    everybody out in alberta where i live use the melling hv55 pump and they work good for most people, that is why i ordered the melling pump....the pump that is in it has no name as whose pump it is and the numbers on it mean nopthing unless you know whose pump it is


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