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Oil pressure

Discussion in 'Chevy Trucks' started by nachoschevs, Apr 7, 2004.

  1. nachoschevs

    nachoschevs Member
    Messages: 58

    Hi all,
    I have a question about what oil pressure you guys usually run on your chevs. I have a 94 4X4 with the 350. It had 120,000 or so miles on it when I got it and the pressure seemed low since I got it. What do you all run on average. When first started it is around mid gage. I have not seen the truck for a while so I am guessing at numbers. Probley around 30 psi or so. When the motor warms up it goes way down to almost 0 psi. This is in gear while idling. When you give it gas and drive it goes up a bit, but still around 10 psi or so. Does this sound wrong or is there a problem with my main/rod bearings. This would be the only reason I can think why it would be so low. Maybe it is time to replace them. I run 10W30 in winter and 10W40 in summer. Any help would be appreciated.
    Nacho
     
  2. ratlover

    ratlover PlowSite.com Addict
    from IL
    Messages: 1,325

    When I think I have a problem with things being outa the norm I first get another guage on it to verify the reading. Totaly independednt, different sender and all. Then once you decide if you actually have a problem then you can work at fixing it.

    On a bright note your truck wouldnt live very long with this kinda oil pressure so I would say the guage/sender/or wiring is fubar. Or you got a small block that just wont die
     
  3. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    If you confirm the oil pressure is low and you aren't ready to rebuild the engine, drop the pan and oil pump. Wash it out thoroughly. On the side of the pump will be your relief valve, its a spring and plunger held in with a rollpin. You'll need to take the four bolts out of the pump to remove it (small pin punch and hammer) Don't lose it! Head down to your local GM dealer and pony up the 5 bucks or so to buy a Chevy High-Pressure pump spring (I think they were used on Z28's and LT-1's from the early 70's and late 60's) and swap it into your existing pump. When the engine is new a stock pump with this spring will make 60psi at around 2000RPM as opposed to about 30 stock.

    May be all you need to extend the life another few years and its a piece of cake (as long as the pan can be dropped in your chassis that is!)

    Derek
     
  4. 84406

    84406 Junior Member
    from canada
    Messages: 17

    I would vote for the relief spring. Good chance that a regular spring would also work as over the years they seem to loose their tension. I have bought many old trucks over the years with poor oil pressure and got them for next to nothing and put in a new spring and instant daily driver. Also possible to put a small washer between the roll pin and the spring. While you have it out check the plunger for free movement as they can be sticky with wear and with a weak spring the plunger stays down the passage. If you want to get real spendie, throw in a new pump as they are quite cheap. If you haven't done it before look into a one piece oil pan gasket as it makes re install much easier when the motor is in the truck.
     
    Last edited: Apr 19, 2004
  5. ratlover

    ratlover PlowSite.com Addict
    from IL
    Messages: 1,325

    as a general rule of thumb a SBC needs 10 psi or so per 1k rpm to live. 10 psi at 2500 rpm or so it wouldnt live long and would probably sound pretty neat when running ;) 0 pounds while ideling would also make her sound pretty scary, you can get buy with a shade over 5 if the motor was built to take it, but it needs to be disigned as such and pressure should build quickly and I wouldnt let it idel for extended periods, this is aint a take grandma out for icecream kinda motor.

    Worn cam bearings ussual cause bad oil pressure reading, or the pump, or bad guage, or other wierd cross leaking type problems and other stuff but the latter is stuff to do with the build Main/rods dont ussualy have an effect on pressure but it definatly effects em!

    If your motor when hot is ideling at near 0 and the lifters arnt ticking like hell and other scary expensive noises arnt going on and the thing actually runs I would say that there probably isnt an actual problem with pressure.
     
  6. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    Guages aren't always accurate. If it is still running there IS some oil pressure, even if the guage says 0 like my old 305. No noises or anything. But what you can bet is if a mechanical oil guage says 0 it means very little oil pressure..... some.... not much. The spring will definately help and will only be an improvement for very little outlaid cash or effort. And we all know what a siezed up engine will cost in both finacial terms and the fact that it usually puts the truck down when you need it most.
     
  7. ratlover

    ratlover PlowSite.com Addict
    from IL
    Messages: 1,325

    Agreed, there may be oil pressure and a differrnt pump or spring would most likely be the fix.....I just would want to know exactly what the oil pressure is and all that before I droped the pan. The pressure may or may not be fine. And even though droping the pump and pan isnt that hard a job its still a PITA. I like to do as little work as needed and save me from possibly doing unneeded work. ;)

    When trouble shooting I always
    1. Verify the problem as an actual problem(no sense fixing something that aint broke, and its hard to figure out what the root of the problem is at times if you dont know exactly what the deal is)
    2. When you must start throwing parts at something start with the cheapest and easiest part to replace and or a part that it wouldnt hurt replacing anyway(like in this case the guage is probably fubar and even if there is a problem it will only read a shade higher and it wount hurt to get the thing reading accuratly)

    As was said, factory guages are ussualy crap in the way of getting an actual reading about anything. But they can be helpfull for telling you when your motor is operating out of its norm. If the guage is telling you something different than it normaly does in a particular situation then I would think things arnt going right. But you cant really tell that your motor is running 250deg because the guage says so....just that its running hotter than it normaly would. Even if I have a aftermarket guage I will double check things......unless it says no oil pressure and the thing is knocking like hell and it siezes up.....then you can believe it;)

    Just the way I do things......
     
  8. nachoschevs

    nachoschevs Member
    Messages: 58

    Hey all,
    Thanks for all the good information. I double checked with my dad back home on what the actual readings are. When first started it is around 40psi. After you run the thing for a while probley about 1/2 hour or so if you come to an idle it is around 10psi. When you put it in gear and hold the break at an idle it goes to roughly 5psi or so. The motor seems to run good since I got it and never gave me a problem for the time I had it. When I get back to the states I will probley take the idea of a different gage and see what it really runs. Then if it is really that low I will go with the high-volume oil pump. That will defiantly solve the low oil problem.
    Nacho
     
  9. The Boss

    The Boss 2000 Club Member
    Messages: 2,099

    Never fully count on the gauge.:waving: