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oil pressure question???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by K5RON, Oct 20, 2001.

  1. K5RON

    K5RON 1/2 ton status

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    Recently, I changed my 305 to a Goodwrench "Universal" 350. The oil pressure at idle after warm-up is 45 lbs. and at highway cruising is 60 +lbs. Some other particulars are 10-40 oil, Pure One filter and I replaced the oil filter by-pass with a Perma-cool conversion adapter. I'm starting to get some minor oil leaks that I attributed to high oil pressure. Am I correct? Is the 60+ too high? The old 305 used to idle at about 13 lbs. Could the oil filter bypass relief thingy give me high oil pressure? I'm thinking not cause it only eliminates by-passing the oil filter. Could the oil filter be too restrictive and cause high oil pressure? Does the guage read "pre" or "post" of the filter? Is the 40 weight oil too thick? Any small-block gurus out there?


    Ron


    '84 K5......Tree Fitty, SM465/Np205, D44/14BFF, Pro-jection! .....and of coarse no other color than Odie!
     
  2. coopertwpk

    coopertwpk 1/2 ton status

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    no that sound right on the money ,13 is way low.

    88k5 silverado w4"lift <font color=orange>d44 and corp14ff</font color=orange> with 4.11
     
  3. BigTex

    BigTex 1/2 ton status

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    Keep in mind that newer engines will have higher oil-pressure. My rebuilt 350 w/60k shows a reading of around 50.

    <font color=red>"SETTING OFF ALARMS IN A CITY NEAR YOU!"</font color=red>

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  4. dragricinMT

    dragricinMT 1/2 ton status

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    Sounds like your new engine has a hi-volume/hi-pressure oil pump. A standard pump at idle will read 15-20lbs normally. Hi-vol pump will read 30-40lbs at idle when motor is at operating temp.

    78-K5 4"Lift 35"Tires 400SB TH350 NP205
    73 Vega 350SB TH350
     
  5. 84_Chevy_K10

    84_Chevy_K10 Banned

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    If you have an electric gauge, I wouldn't trust it anyway.

    If you've got oil leaks on a new engine, you've got a problem, and it's not related to oil pressure most likely.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  6. 84_Chevy_K10

    84_Chevy_K10 Banned

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    If you have an electric gauge, I wouldn't trust it anyway.

    If you've got oil leaks on a new engine, you've got a problem, and it's not related to oil pressure most likely.

    And as for the high pressure or high volume pump, the reading that you'll get at idle depends on a lot of factors, including the oil weight and the bearing clearances, so there's no general way to say that you'll get 30 or 40 psi at idle. I run 5W-30 synthetic oil right now and only get 15 lbs of oil pressure at hot idle.

    Be careful with 10W-40 oil, that could void your engine warrenty. Engine manufacturers don't like 10W-40.

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

    chevyracing 1/2 ton status

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    Spend 20 bucks and get a 2 nd gauge (mechanical) and hook it up at the front of the engine above the t-chain cover where the little plugs are. See if the readings are the same. If you have that much oil pressure you will wear the main bearings out so fast it will make your head spin. As far as too much pressure causing the engine to leak, doubtful, most gaskets to the outside of the engine are not on a pressure side of the oil. A likely cause for the engine leaking at the gaskets is the block breather being clogged or covered. That will create a vacuume inside the engine that can weaken the seal on the gaskets causing splash oil to saturate and make it past them.
    A small block Chevy with too much oil pressure will push the crank downward into the main bearings causing too much "dry" pressure and prevent enough oil from getting on the cap side of the bearings. This is a very argued point, but makes sense to me.....
    As far as a possible cause the spring in the oil pump may be too heavy or stuck. You can get a new spring and plug at most parts stores for about 8 bucks.

    John


    Like to go sloppin' 'round in da mud in a rapid fashion....=) [​IMG]

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  8. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    The only place that a oil leak from to much pressure would be noticable as a leak would be the rear main seal. Also the new motors run tighter tolerence and designed to run on 10w30. I run 10w30 in the winter on the crate in my wifes truck. Oil pressure is close to the same readins as your seeing in the summer with 10w40. not quite as high on the hwy. I usualy see about 50-55 psi. about 35-40 idle hot. That is on a factory gage with questionable acuracy.
    Now one thing I noticed about my crate when I got it was the valve covers were WAY overtightend. The gasket was crushed and the covers were warped at the holes and it had developed a valve cover leak as a result. I took them off got it back straight with a little time with a hammer and bench vise. Put new gaskets on it and put a set of cover hold down distribution tabs on it. you can get them at Autozone for pretty cheap on the hot ro section. Made by Mr.Gasket. Chrome peices that go in before the bolts about 3.5 inches long.
    Be sure to spray some brake cleaner on paper towel and whipe down the sealing surfaces to make sure they are oil free before installing the new gaskets. If there is oil there then the gasket will not seal to the head or cover.

    Women dig dents and flat paint!
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  9. K5RON

    K5RON 1/2 ton status

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    Well, I have a factory guage and it's very near 60 when cold and at the 45 mark or above when idleing. I'm gonna try a 10-30 or a 5-30 oil. Its seems to be leaking(albeit slight) at the head gasket or somewhere above the starter. It's really tough to detect where it's coming from but it usually drips on the front diff!

    Thanks for the replys,


    Ron


    '84 K5......Tree Fitty, SM465/Np205, D44/14BFF, Pro-jection! .....and of coarse no other color than Odie!
     
  10. 2cocky

    2cocky Registered Member

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    I'm running the same GM goodwrench 350 and i see about 55 on start up and 40 at hot idle. btw i'm running 5w-30

    OOOPS....I THINK I JUST RAN OVER YOUR JEEP THING!!!!!
     
  11. dragricinMT

    dragricinMT 1/2 ton status

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    don't mean to be rude but how do you wear out main bearings with to much oil pressure{oil pressure mentioned above}? Not enough will wipe them out, but I'vs seen pressures up to 100psi not wear out bearings.

    78-K5 4"Lift 35"Tires 400SB TH350 NP205
    73 Vega 350SB TH350
     
  12. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    There is no way to get a oil leak at the head gasket unless the head is about to fall off. There are only drain back passages through the head. No oil under pressure in the head. The oil for the rockers comes through the push rods. It's oil that purges from the lifters and squirts through a tiny hole where the ball on the push rod mates to the rocker arm. My bet is a valve cover leak at the back. that's were mine was leaking. If it's not there then you may have a leak at the intake (Very rare) or where the sender for the gage is in the oil passage right behind the distributor. Could even be a bad sender that is leaking.
    99% chance of it being the valvecover gasket. $20 and a bunch of cussing pulling loose the A/C mount and the air pump crud to get to the cover.

    Women dig dents and flat paint!
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  13. Burt4x4

    Burt4x4 3/4 ton status

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    One thing that hasen't been metioned yet is the PCV.
    When I first got my K5 I started playin with the differnt vac sources hooked to my carb. Well my brain and I had some great idea to just cap the PCV on the valve cover and plug the vac source on the carb. So I did and started down the road for a test drive. Suddingly as I got up to speed I noticed my oil press had passed 60???what??? THEN pooff!!! A tone of smoke started comming out of my engine bay!! Damn oil spillin out onto my headers and everywere else!!
    So I put the PCV back on and now my HWY pressure is 50 and idel about 35, no more oil goin everywere........
    Just thought I would share that learning experance.


    72K5[​IMG]Led Zeppelin[​IMG]Rock ON![​IMG]
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  14. BARRAZA

    BARRAZA 1/2 ton status

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    Small block Chevies have an excellent standard oiling system and one built with the proper clearances should have exactly the pressures you describe, don't worry. The pressure reliefs in the pumps open at approximately 40 psi, so pressures less than that mean that the pump can't keep up with the internal leakages, ie mostly from main and rod bearings. 60 psi is not excessive, but the guages are notoriously inaccurate. A general requirement for small blocks is 10psi per 1000 rpm.
     

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