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oil pressure, oil pump?

Discussion in 'The Garage' started by pvfjr, May 3, 2004.

  1. pvfjr

    pvfjr 1/2 ton status

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    My oil pressure is fine when cold or at higher rpm's, but at warm idle it drops severely. I have a suspicion that it is the main bearings allowing the oil to pass through too easily, but I would love it if someone could tell me I'm wrong. The next time I pull this engine will be to replace it, but I would like to get more miles out of it. Could I get by with replacing the oil pump? Possibly with a high volume one?
     
  2. schmuck

    schmuck 1/2 ton status

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    you could try, but i dont think it will help, ive seen an engine with the same caracteristics kepp running for 6 years and it hasnt stopped yet
     
  3. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    Mine reads a little low warm, and I can't kill it. As they wear out they drop in pressure. A properly built Chevy engine will live with 10 psi and not die. /forums/images/graemlins/k5.gif
     
  4. m j

    m j 1/2 ton status

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    it isnt much more work to stuff main bearings in it vs changing the pump
     
  5. 4xcrazy

    4xcrazy 3/4 ton status

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    I dunno, /forums/images/graemlins/dunno.gif but with over 211,700 miles, i'm still pushin over 35some psi at warm idle.
     
  6. pvfjr

    pvfjr 1/2 ton status

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    What about 0? Not as good as 10. Can't I change the pump without pulling the engine? Replacing the bearings would involve practically a complete teardown wouldn't it? As opposed to just the oil pan. Or is it that simple?
     
  7. tarussell

    tarussell 1/2 ton status

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    It is possible to drop each main cap one at a time and roll the old top bearing half out and roll the new top half in by using a "soft" nail with a large head ( or something similar ) to grab the bearing. just use the oiling hole in the crank for nail placement and rotate in the direction that the tang, in the bearing, will not get caught in the main saddle.All of this can be done with the engine in the truck .

    If I were you I would pull the mains and inspect the bearings - if they are shot than you have problems and bearing and pump replacement is just a bandaid and a rebuild will be needed soon. If the bearings are not down to the copper than you might get some more time out of that engine with new bearings and pump and "thick" engine oil .
    Good luck , Tom
     
  8. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    I was just talking about this with the machine shop where I had my motor done. He said they get this all the time.

    Is the gage electrical?

    If so, switch to a mechanical gage. He said most of the time the oil pressure is just fine with the mechanical gage. It has to do with the heat affecting the electrical sending unit.
     
  9. pvfjr

    pvfjr 1/2 ton status

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    Yeah, its electrical. It does tend to jump around a bit too. I just tought it wasn't lying because of how consistant it was with the temperature and engine speed. I'll see where I get with a mechanical.
     
  10. k20

    k20 3/4 ton status

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    well w/ my 350 I had 0 pressure at idle, bout 30 runnin down the road, after she let go on the tear down, bearings were wore all the way down into the copper, one almost through /forums/images/graemlins/yikes.gif and rings were mostly nonexistant. She was tired. It only had 144k on it.
     
  11. pvfjr

    pvfjr 1/2 ton status

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    That's what I'm afraid of. I'd like to get a few more miles out of it before I replace it. I have a big trip coming up and it's making me a little nervous though. Especially since the clock is ticking and I'm still finishing up this tranny conversion.
     
  12. diesel4me

    diesel4me 1 ton status Premium Member

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    The 400 small block in my 74 K20 plow truck only shows 12 psi at idle hot,about 33 psi over 2000 rpm (mechanical stewart warner gauge)and its been this way since 1990.I admit I dont drive it hundreds of miles,and it rarely sees the highway,and the motor has always had a few ticky lifters also it burns some oil too,especially when you start it first time in the morning.But it hasnt spun a bearing yet,and I sometimes wind it up higher than I should!.I would not loose too much sleep over low oil pressure as long as its doesnt rap.Mine doesnt "dry knock" when first started cold yet--when you hear that little "woodpecker" noise on a cold start,you dont have much time left on the bearings.A new oil pump and or thicker oil will help delay the inevitable,but it is a band aid as others have stated.I have had several chevys that were the same way,and the only thing I have had trouble with on theese high mileage beaters has been timing chain failure on long trips(due to the factory nylon junk cam gear shedding its teeth,and clogging the oil pump screen)and camshaft lobes going flat.Other than that,a good chevy motor is pretty hard to kill!. /forums/images/graemlins/grin.gif
     

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