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Oil Pressure Range - thoughts?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by rem7600, Jul 5, 2002.

  1. rem7600

    rem7600 1/2 ton status

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    Hey all,

    Been a long time since I posted here. Still have my relatively stock 89 Jimmy. Small Lift, 33's, 350tbi, oil cooler, and all the standard stuff.

    Oil pressure is dropping as low as 15 at an idle. At any sort of RPM (daily driving) it's holding right at 30-32. Factory guage, sending unit etc.

    158,000 and counting. Any thoughts? I was always brought up that 32 on the noggin' was where you wanted to be. I run QS 10W-30 4X4 Synthetic Blend (And I KNOW the 4X4 doesn't mean it's that much better) :-) Or wait, DOES IT? The rear main leaks a little, but not bad at all. Find a chev with that many miles that doesn't! :-)

    Anyhow, what are your thoughts on the 15psi? Possible causes? Rod Bearings? :-( faulty sending unit :-) Let's hear any suggestions you got!

    Thanks

    REM7600
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Oil pump and bearing clearances affect your oil pressure. Minimum pressure should be 10 psi for every 1000 rpm, so 15 psi at idle is still OK. At 158,000 miles the bearings and oil pump will both be somewhat worn causing the lower oil pressure. When I got my truck with 40,000 miles on a rebuilt 350 I had 35 psi at idle and 50 or so at cruise rpm. Now at idle it's about 20 or so and about 30 at cruise rpm. The motor now has about 110,000 on it. When I replaced the rear main seal a while back I noticed some wear marks on the bearing surface/forums/images/icons/shocked.gif...it still runs strong though.

    Rene
     
  3. jc71355

    jc71355 1/2 ton status

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    My 91 has 190,000 on it and it doesn't leak a drop or burn a drop /forums/images/icons/grin.gif . My dad has a 95 Z71 that burned a quart of oil inbetween changes from the day he got it till it turned 100,000 then it quit, i guess the motor finally broke in /forums/images/icons/tongue.gif . I run about 50 or so cruising, probably closer to 40 idling.

    James
     
  4. tori89k5

    tori89k5 1/2 ton status

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    Like Rene said..... 10 is fine, and 15 is actually nothing to worry about either. Just keep doing what your doing, and dont worry about it for several thousand more miles. /forums/images/icons/smile.gif
     
  5. 79Beast

    79Beast 1/2 ton status

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    IN MY OPINION........15psi at idle is fine.....if you are talking about operating temperature. If you are that low when you first crank it up, you have problems. I assume you are running a factory motor with factory oil pump. I built my 350 in the summer of 99. It has a sealed power high pressure pump and runs as high as 60psi idling at 700RPM when the motor is COLD. When it is good and warm, it will have about 20psi. I run Valvoline Durablend 10W-30, but I don't have an oil cooler. As long as the pressure goes up when the RPMs do, don't worry about it. On a motor with the miles yours has, as long as there is oil pressure, you're good.
     
  6. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    My old man has BRAND NEW one piece rear seal crate 350 in his '89 Jimmy. When its fully warmed, it will put out about 15 psi.

    My new 355 will do 31 at idle fully warmed and 60+ when cruising (2,100 rpm).
     
  7. 70~K5

    70~K5 1/2 ton status

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    Blazer Boy have your old man hook up a mech. oil press. gauge to his motor. If those numbers are right then he beter be talking to whoever he bought that crate motor from. Cause that ain't right.
     
  8. Twiz

    Twiz 1/2 ton status

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    I'm gonna jump on the boat too and say 15s O.K. - 10 for every 1000 is the rule of thumb.

    I don't remember the factory specs off the top, but I know the minimum PSI was really low, single digits if I recall. Low enough the think "Yikes!". The blocks are set up loose, I would guess it might be to slightly increase the MPG rating.
    I know it sounds goofy, but the manufactures do alot of goofy stuff that would appear to be strictly fuel economy related (at-least as far as I can tell).
     
  9. 70~K5

    70~K5 1/2 ton status

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    I took it as Blazer Boys dad's motor has 15 lbs max, if that's the case then something's wrong there. If it's 15 at idle then disregard my post. /forums/images/icons/confused.gif
     
  10. 90K5

    90K5 1/2 ton status

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    32 sounds a little low for cruising, mine runs about 45 with 160,000 on the clock...I also use 20w-50 though, but even when I ran 10w-30 last winter it was about the same.
     
  11. 91K5

    91K5 1/2 ton status

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    My '91 with 174,000 miles runs about 55 psi at idle cold, about 40+ all the time after warm. My old Blazer with a 305 had about 10 psi at idle, 15-20 most and it never died so I think your OK. Chevy's are venerable enough to take it in my opinion.
     
  12. rem7600

    rem7600 1/2 ton status

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    I want to thank everyone for the replies...
    I read through each and every one. It sounds
    as though a few of you are having better results
    than mine, but I don't have to worry for a while
    yet. When my rig starts I'll have 40+ showing on
    the guage. Only when it's really hot out (90 plus)
    here in the Northwest have I seen real drops to 15ish
    at idle. I'm a natural worrier...

    What about 90K5's thoughts of running a heavier oil in
    the heat, good bad, indifferent? No offense 90K5 just
    would like some other opinions on it.

    REM
     

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