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HI-vol oil pump and 20psi?

Discussion in 'The Garage' started by bigarmzz, Sep 7, 2006.

  1. bigarmzz

    bigarmzz 1/2 ton status

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    i bought a melling hi vol oil pump for my 87 tbi, oil pressure is through the roof at start up, but after it warms up, it only has like 20psi...???:confused:

    i got mechanical gauges, so i know this pressure to be accurate...any ideas?

    (just hoping i dont have spun bearings or anything):( the motor runs like a power house

    i did a compression check on the cylinders as i was curious, here's the compression:

    8-155 1-160
    6-160 3-175
    4-175 5-175
    2-150 7-175
     
  2. 1985_K5_Silverado

    1985_K5_Silverado 1/2 ton status

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    Was the oil pump the only thing that changed on the engine? If so, what pressure was the engine running with the old pump, under the same conditions? How many miles are on the engine?
     
  3. bigarmzz

    bigarmzz 1/2 ton status

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    yeah, stock motor

    before the hi vol install, it was reading (with the stock gauges) around maybe 12-15psi when warm, thats why i wanted the hi vol setup....but now its not reading that much more than it was before..... for some reason

    motor's only got (supposedly:rolleyes: ) around 80k on it, which may be, cause it has good compression of all cylinders, and is real clean inside
     
  4. rcamacho

    rcamacho 1/2 ton status

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    What's the oil pressure at idle and with RPM's? 20 PSI at idle is not too bad. If you want more pressure you may need to step up oil viscosity. Internal bearing clearances could also be loose, thus causing a drop in pressure.
     
  5. neverendingproject

    neverendingproject 1/2 ton status

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    You wanted a high pressure, not a high volume. When warm I have like 50psi with 15w-30. At rpm, my guage doesnt go high enough.
     
  6. TWISTEDJACK

    TWISTEDJACK 1/2 ton status GMOTM Winner

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    I have the same pump on mine at idle warm it is 20 but as soon as it comes off idle it jumps to 50 that is with delo 15w-40. Seems nomal to me if you want more pressure get a diffrent pump.
     
  7. bigarmzz

    bigarmzz 1/2 ton status

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    yep, thats what i was wanting:rolleyes:
     
  8. sweetk30

    sweetk30 professional hooker Premium Member

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    10lbs per 1k rpm. and idel is around 750-850 rpm so around 10-15 psi is perfect. did you get the hardened and pined shaft to go with the hv pump?

    and if you have 20 at idel warm wow thats great.

    oil is thick at cold = much more pressure

    oil is thinner at temp = less pressure

    try sucking a thick milk shake threw straw and then suck water threw same straw. same basic idea. flows better when warm.

    why do you need so much oil volume and pressure. you need to make sure you dont starve the pick up with these pumps . comon problem under 4x4 conditions as thay suck a lot more oil. and did you tack weld the pick up in the pump?
     
  9. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Hi volume only increases the amount of oil it moves not the pressure of the oil. The only thing that affects oil pressure are bearing to crank clearances and cam to bearing clearances and also pressure relief spring in the oil pump. My rig has 231K on the original engine (never been apart yet) and cold it pegs the gauge at 60 plus psi and running temp it sits right between 55-60 psi.
     
  10. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    My stock motor with 160,000 miles on it gave 30psi, hot, cold, idle or 4000rpm. When I rebuilt it I put a new oil pump in, can't remember the make, and now it is pegged out when cold, even at idle, but when hot gives 20psi at idle and around 45 or so at higher revs. That's with 5w30 mineral oil. (which I've always used)
     
  11. mouse

    mouse 1/2 ton status

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    The Melling pump in mine behaves similarly. Its got 700 miles on a new crank/crank bearings. At start up it pegs the gauge, once warm, at idle, around 30.
     

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