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oil pressure

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by MUDNUTT, Sep 22, 2001.

  1. MUDNUTT

    MUDNUTT 1/2 ton status

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    need some help. i recently put together a 350 and have a problem with oil pressure. when i first start it, it has 50 or 60 lbs, once it warms up going down the road it has 30lbs, but at idle once its warm the guage says it only has about 3 or 4lbs. i replaced the sending unit with no change. i have a mechanical guage to put on to verify the electrical but cant put it on till tomorrow. sorry this is so long but its kind of scary to only see 3lbs on a motor you just rebuilt

    <font color=blue>DRIVE IT LIKE YOU STOLE IT[​IMG]
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  2. Dependant on what the max pressure of the gauge is (60 psi?), it can't accurately gauge between 0-8 psi, that is just the nature of gauges. To get a accurate 0-5 psi reading, the max working pressure of the gauge would only be 15 psi! Obviously, you do not want a 0-15 gauge on your oil pressure. As maybe you can tell, I deal with gauges on a daily basis. A mechanical gauge will give you a more accurate reading, the electrical gauge on my 86 does about the same thing as you are describing. I have attributed it to a worn out gauge and some electrical shortcomings.

    God has a hard on for Marines, because we keep Heaven chock full of fresh souls!
     
  3. chevyracing

    chevyracing 1/2 ton status

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    Hey Bob, (er...mudnutt)
    Loose nut behind the wheel. Maybe it's the throwout bearing..LOL!!!!!!! See ya tomorrow Bro.

    John


    Like to go sloppin' 'round in da mud in a rapid fashion....=)
     
  4. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I wouldn't trust an electric guage to tell me much more than if my engine had oil pressure or not!!

    Spend $8 and get a mechanical gauge. I bought mine at Wal-Mart. I am planning on putting all Autometer in my dash soon, but I figured that putting a couple gauges in there that were cheap for now would work until I buy them.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  5. MUDNUTT

    MUDNUTT 1/2 ton status

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    ttt

    <font color=blue>DRIVE IT LIKE YOU STOLE IT[​IMG]
    <font color=red>PROUD TO BE AMERICAN[​IMG]
     
  6. POWERMAD

    POWERMAD 1/2 ton status

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    have you hooked up the mechanicle gage to verify that the other gage is accurate?


    <font color=green> Too bad ignorance isn't painful </font color=green>
     
  7. POWERMAD

    POWERMAD 1/2 ton status

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    Also what kind of rebuild did you do?
    Did you check the clearances on the main and rod bearings?
    Did you pre lube the system before you fired it up?

    <font color=green> Too bad ignorance isn't painful </font color=green>
     
  8. muddin4fun

    muddin4fun 3/4 ton status

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    I would guess the guage is bad. Hook up the mechanical guage when you get it and let us know what it reads.

    If you see my truck on a trailer, call 911 cause it's <font color=red>STOLEN!!!</font color=red>
    Website link is in my profile [​IMG]
     
  9. RaisedK5

    RaisedK5 1/2 ton status

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    I actually have the same problem right now, so i hooked up a different gauge, same deal plenty at startup, plenty of pressure under power, at idle nothing, both are mechanical, soooo out comes the shop manual, "No pressure at idle" 1. oil level, (duh), 2. Pump not functioning properly, (regulator ball stuck b/c of foreign matter) 3, too much clearance in Main or rod bearings , 4, loose cam bearings, 5, blocked pick up screen. soooooo if those are my only options, i think i'll replace the pump and see where to go from there, I always wanted a better pump anyway, at least thats what i'll keep telling myself as oil is running down my arm next sat.

    Leland aka RaisedK5

    "Of all the things I've lost, I think I miss my mind the most!"
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  10. newyorkin

    newyorkin 1 ton status

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    C'mon now, what's wrong with <a target="_blank" href=http://coloradok5.com/gallery/NewYorkin/aag>a little oil runnin down the arm</a>?

    I had the same problem, and replaced the pump with a brand spankin' new high pressure pump. There was an immediate improvement in consistent pressure (not to mention about double the normal pressure)... I was going to do the bearings while I had it open in case they were the true problem, but I opted not to for lack of the proper torque wrench handy, and it appears they were fine. If you get a new pump, verify the old plastic or nylon sleeve is complete, or you'll need to make sure you find all the pieces before you close it all back up.

    On the rebuilt motor, is it possible your block was line bored and you used stock bore bearings? Did the old bearings have any stampings on them?

    Ratch
    <a target="_blank" href=http://k5.8m.com>k5.8m.com</a>
    **Ever stop to think... Then forget to start again?**
     
  11. MUDNUTT

    MUDNUTT 1/2 ton status

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    got the mech. guage put on with no change. changed the filter bypass spring w/ no change. dropped the pan and pulled a main to verify the clearence. the book called for .008 to .024 and it micked out to .015. when we put it together we used a standard volume pump, so when we checked the main we put in a high volume unit. got it all back together and still no change. any ideas, im about ready to pull out whats left my hair[​IMG]

    <font color=blue>DRIVE IT LIKE YOU STOLE IT[​IMG]
    <font color=red>PROUD TO BE AMERICAN[​IMG]
     
  12. POWERMAD

    POWERMAD 1/2 ton status

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    How did you mike the main with the crank still in the block?
    I am not trying to be a smartass.
    All it takes is one main or rod being too loose to cause low oil pressure.
    Or loose cam bearings.
    Did all of the oil gallery plugs get put back in?
    When I bought my 73 it was rebuilt and they left the cam plug out of the back.
    But that was real obvious as oil was pouring out the back.


    <font color=green> Too bad ignorance isn't painful </font color=green>
     
  13. MUDNUTT

    MUDNUTT 1/2 ton status

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    bought the block from my machinest. he had already had it hot tanked never really checked the galley plugs. where exactally are they at?

    <font color=blue>DRIVE IT LIKE YOU STOLE IT[​IMG]
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  14. POWERMAD

    POWERMAD 1/2 ton status

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    They are 3 pipe plugs under the timing cover. and 2 at the rear of the block.
    When they hottanked it were the cam bearings removed and new ones installed?
    hottanking ruins bearings.


    <font color=green> Too bad ignorance isn't painful </font color=green>
     
  15. MUDNUTT

    MUDNUTT 1/2 ton status

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    if those were the only ones then their all there. yes it has new cam bearing, i got a rebuild kit from summit and my machinest installed them

    <font color=blue>DRIVE IT LIKE YOU STOLE IT[​IMG]
    <font color=red>PROUD TO BE AMERICAN[​IMG]
     
  16. POWERMAD

    POWERMAD 1/2 ton status

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    Hmmmm
    I would have to say it has to be a main or rod out of tolerance.
    Are you using the old crank or is it a reground one?
    Did all the bearings get checked before assy?
    With the crank still in the block plast-gage can tell you if they are close.
    Personaly when I assemble an engine I like them to be at .0015
    Not too loose or to tight.
    My manual says the clearances are
    mains
    #1 0.0008-0.002
    #2,3,4 0.011-0.0023
    #50.0017-0.0032
    rods
    0.0013-0.0035

    <font color=green> Too bad ignorance isn't painful </font color=green>
     
  17. MUDNUTT

    MUDNUTT 1/2 ton status

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    its a steel crank that was ground .010 and the bearings were .010

    <font color=blue>DRIVE IT LIKE YOU STOLE IT[​IMG]
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  18. POWERMAD

    POWERMAD 1/2 ton status

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    Was the block boredout to the next size?
    If it was were all the main caps on and torqued to specs?
    Are the main caps on the right journal and facing the right way?
    BTW I have sent cranks back because they were ground wrong or not the right size.
    I am just throwing out ideas here.

    <font color=green> Too bad ignorance isn't painful </font color=green>
     
  19. MUDNUTT

    MUDNUTT 1/2 ton status

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    block was bored 40 over, ring gap was within spec. all the caps are on the right way[verified today when we had the pan off]. mains were torqued to 65lbs and the rods to 45lbs. a buddy of mine thinks that maybe it has an internal leak!

    <font color=blue>DRIVE IT LIKE YOU STOLE IT[​IMG]
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  20. chevyracing

    chevyracing 1/2 ton status

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    Hey Bob,
    Looks like you have been after it on here. As much as I hate to say it, it looks like you and I are going to be back in my garage again yanking that thing out and hauling it to Gary's house and asking him what the phuque????? I know we put it together right.......Definately bumming me out too Bro. Ciao' til in the morning.

    John

    Like to go sloppin' 'round in da mud in a rapid fashion....=)
     

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