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  1. #1

    Default 350 TBI - Very High Oil Pressure and Loud Tick

    It's a '94 Suburban K1500 with ~215K. The motor has always run strong (not sure if it is the original, or has been rebuilt by previous owners) and showed no signs of any problems. Earlier this week it started ticking loudly on start up, but would smooth out after idling for a few minutes. Yesterday, I noticed that the oil pressure gauge pegged itself out on start up, but returned to normal after a minute or so of idling. Today, it did the same thing when I left the house, but on the return trip, the pressure wouldn't drop back down and blew the gasket on the oil filter. I went and got a new oil filter and replaced the old one (what a f***ing mess to do in a parking lot) and it did the same thing after only idling for 30 seconds.

    Needless to say, my truck is sitting in the parking lot at my brother's work. Hopefully I don't have to tow it home, it'd cost an arm and a leg with how far it is.

    Any ideas guys and gals?
    Scott

    ΜΟΛΩΝ ΛΑΒΕ

    '94 Chevy Suburban K1500
    3" exhaust w/ aero turbine non-baffled muffler
    CFM Technologies TB spacer
    CB w/ 44" whip antenna


  2. #2
    Jr. Apprentice spottweld's Avatar
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    Default oil pressure

    It sounds as if your filter housing is not bypassing. take your filter off and you will see two bolts up there between the stud that the filter screws on. That is your oil pressure bypass and it is usuallly set around 15 psi, yes not all of your oil gets filterd every time it is circulated. There is a little check ball and spring inside the housing and if that gets stuck open your filter will get the full pressure and blow something out. It sounds to me that your filter is not on that tight if it was it could have blown a hole on the filter. If you look on summit or jegs you can find special filters and non bypass filter adapters. This is an easy fix and you dont need any gaskets, just pull out the two bolts and the filter adapter will come right out and go to the junk yard or aout parts store and get a new one
    I am an enthuasist who is starting my life over. Keep an eye on me for i will have a lot of parts for sale in the future, let me know and i will keep an eye out for you. older trucks only 87 and older, especially 68-72.
    Jeremiah

  3. #3

    Default

    Couldnt even guess why the oil pressure is staying high. Possibly some of the oil galleries got blocked.
    The high oil pressure has probably damaged the seals on the hydraulic lifters and thats where the ticking is coming from, I've seen it happen before on an older engine.
    In that case they had just replaced the oil pump.

  4. #4

    Default

    Quote Originally Posted by spottweld View Post
    It sounds as if your filter housing is not bypassing. take your filter off and you will see two bolts up there between the stud that the filter screws on. That is your oil pressure bypass and it is usuallly set around 15 psi, yes not all of your oil gets filterd every time it is circulated. There is a little check ball and spring inside the housing and if that gets stuck open your filter will get the full pressure and blow something out. It sounds to me that your filter is not on that tight if it was it could have blown a hole on the filter. If you look on summit or jegs you can find special filters and non bypass filter adapters. This is an easy fix and you dont need any gaskets, just pull out the two bolts and the filter adapter will come right out and go to the junk yard or aout parts store and get a new one
    Is this a job that I could do in the parking lot, or do you think I'm going to have to tow it home? Also, would this cause the pressure gauge to peg out at max. and stay there?
    Scott

    ΜΟΛΩΝ ΛΑΒΕ

    '94 Chevy Suburban K1500
    3" exhaust w/ aero turbine non-baffled muffler
    CFM Technologies TB spacer
    CB w/ 44" whip antenna


  5. #5
    Legend unplugged's Avatar
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    Default

    There are two oil bypass points in reference to the oiling system on the SBC engine. The filter mount has a built in bypass in the event that you do not change the filter at the recommended interval and the media is clogged, the oil will bypass the media and return to the engine. This also happens at colder temperatures. (Dirty oil is better than no oil)

    The other bypass located in the engine oil pump and is mentioned in this article from: www.highperformer.com

    The question is which pressure relief valve is not working? The engine or filter bypass? For $20 you can buy a replacement filter mount that has a new bypass valve. If that doesn't work you'll have to consider pulling the pan to replace the oil pump.

    GM filter mount with bypass valve


    Highperfomer.com

    Oil Pump Function in Chevy 350 Engines


    When the engine rotates at approximately 3,000 rpm there is bound to be frantic and violent movement of the pistons inside the engine. At the same time the crankshaft is spinning swiftly. Even the rocker arms are rapidly moving in two-steps with each respective valve. No matter whether the Chevy 350 engine is just sitting idle in the drive or rapidly moving at full-throttle, what it requires is a good lubrication system.
    Oil needs to be directed to all of the metal contacting surfaces. This is possible through a full-pressure lubrication system comprised of an oil pan, an oil pump, several quarts of oil, and a series of passages inside the engine. An oil reservoir is to be found directly below the crankshaft with internal passages within the cylinder block, crankshaft, and openings in the cylinder heads. A 1/2 inch and 5/8 inch diameter oil pump inlet on small-block and big-block engines respectively, with an adequate suction screen submerged in engine oil, provides free-flowing oil to the pump. The pump is driven by the camshaft. The oil supplied to the pump makes its way through a full-flow oil filter into a 1/2 inch main gallery on a small block. The main gallery is positioned above the camshaft. The lube travels from there through a hole to the groove situated nearby the rear side of the rear cam bearing. This is the position where the lifters and rear main are oiled. The four front cam bearings have grooves that pass to each individual main bearing. Oil passes down into the crankshafts main journals through tiny holes in the upper main bearings. From the main journals it travels to the rod journals.
    At the time the above action is taking place, the crankshaft is continuously spinning. And each rod connected throws oil onto the respective cylinders. This is not only to lube the moving pistons and rings but also to help seal combustion. Oil travels from top of the engine down to the springs and valve stems. And there it helps in lubing the valve stems as they budge about in the valve guides. A relief valve is responsible for circulating the oil back to the inlet side of the pump. This helps to keep the pressure from getting too high at the oil pump. At even higher engine speeds, the moving oil might whip the crankshaft and cost power. This is called as windage. To minimize windage, install a windage tray to turn the oil away from the spinning crankshaft.
    Here is a diagram of the oil flow described above:

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  6. #6

    Default

    You rock man. Thanks for the info.! Looks like I'll be towing her home tomorrow and crossing my fingers I don't have to drop the pan. Might be a good time for some upgrades (if I can find the cash....).
    Scott

    ΜΟΛΩΝ ΛΑΒΕ

    '94 Chevy Suburban K1500
    3" exhaust w/ aero turbine non-baffled muffler
    CFM Technologies TB spacer
    CB w/ 44" whip antenna


  7. #7

    Default

    Okay. I finally had time to pull the oil filter mount out. I was playing around with it and found that the port in the picture was stuck close. When I pushed on it with a screwdriver it popped open with some effort and now it moves open to close and vice versa very easily. Is this the by-pass port that was causing me problems? Did I just fix the problem maybe?

    Scott

    ΜΟΛΩΝ ΛΑΒΕ

    '94 Chevy Suburban K1500
    3" exhaust w/ aero turbine non-baffled muffler
    CFM Technologies TB spacer
    CB w/ 44" whip antenna


  8. #8

    Default Did you ever get your oil pressure/flow problem solved?

    Hey there, did you ever get your oil flow/pressure problem fixed? Was it the filter bypass?

  9. #9
    Master Mechanic Silverado Junkie's Avatar
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    Default

    Hey guys, while we're on the topic, what is the proper oil pressure of a chevy 350?
    1995 Silverado,Z71, 3-inch lift,2-inch leveling kit, SkyJacker Suspension, short ram-air intake, throttle body spacer, MSD ignition coil, straight pipes

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