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Thread: Chevy 350 & High Oil Pressure

  1. #1

    Default Chevy 350 & High Oil Pressure

    The motor in my airboat is giving me a bit of grief. The oil pressure used to run 40psi under power at all temps. Now it's running 80psi under power and 40 psi at idle. My dipstick is popping out and oil is coming out of the valve cover vent tube. I just changed the oil and filter with 5 quarts of 10w40 synthetic. There is no PCV valve or CDR. The only thing I can think of is something is plugged.

    Any suggestions or tips?

  2. #2
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    Do you have a blown head gasget ?????

  3. #3

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    Well, I was told the head gaskets are fine by Kevin @ AK Airboats and I've put about 10 hours on the motor since. I don't have white smoke pooring out of the exhaust, and I'm not loosing coolant excessively. Come to find out the motor was rebuilt right before I bought it. Go figure.

  4. #4
    Member greythorn3's Avatar
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    pvc valve?
    Semper Fi!

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    Member smtdvm's Avatar
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    Done anything to her lately? Like change oil filter etc?

  6. #6

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    No PCV valve. I looked high and low for that little turd, no CDR either.

    The problem started the weekend before last and thought maybe I had water in my oil. The oil was fresh on 6-5, I changed it last thursday due to the high oil pressure and it looked fine. A little dirty for only a couple of weeks worth of use though.

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    Member SusitnaAk's Avatar
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    I have a 350 and run in the 80,s at high rpm One of the valve covers should have hose going in over to the carb.. Ck it for blockage If nothing there, drop the oil & Filter go back to what you had, see if thats it since that only thing that you changed I,m still old school straight HD30W Maybe try just swap for new filter first! I have seen one bad one, Let us know what you find

  8. #8

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    Thanks for the advice SusitnaAK

    What are the chances two oil filters were bad right out of the box?

    Both valve covers have hoses to the spark arrestor and they are both free of blockages.

    Tomorrow I will probably change the oil again to make sure there's no coolant in the oil. Darn it, I suppose it's time to call Leonard and give him and ear full.......

  9. #9
    Member SusitnaAk's Avatar
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    Just never Know if they bought at the same time, Maybe time for wet dry compression Ck, That might tell the story? If getting blow by the rings? Because they didn,t seat or broke one on the break in peroid?

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    Also, do not overlook the easy stuff. There is a chance your gauge went bad.
    Tennessee

  11. #11
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    If you have oil blowing out of your dip stick I would think it would not be your gauge.
    I have a mechanical oil gauge if you want to try it.

  12. #12
    Member Limetrude's Avatar
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    Lightbulb An idea-blown head gasket

    Just a thought, I know there was already a post about it possibly being a head gasket, which was my initial reaction as well. Looking for water in the oil or white exhaust is only a partially accurate way to check for problems. I once had a motorcycle engine that had a blown head gasket, only problem was instead of a water passage being vented to the cylinder, it was an oil passage. Thus the water still circulated just fine and did not mix with the oil whatsoever, but there were some incredible oil pressures (so much so I shot a good share of oil out of every orifice the engine had and some it wasn't supposed to. A less severe leak would result in you simply dirtying your oil rapidly and perhaps even scorching it. Moral of the story is a compression check will tell you much more than just checking the oil for water. I have seen head gaskets blow out on low hour engines (5-20 hours) due to lack of a re-torque of the head bolts after the initial warm up. I don't know the history of your engine, but if it was recently rebuilt or anything, ask yourself or your mechanic if the head bolts were re-torqued and if the threads were super duper clean and free of any oil or rust flakes etc. If they were torque to yield type bolts then they should not be reused. My rule of thumb in rebuilding motors was when first starting them after replacing the head gasket, warm them up to operating temp, shut off, retorque while warm if not aluminum, else if aluminum head, wait until it cools down. Also don't retorque head bolts on an old gasket. Failing any one of these has caused me grief in the past with head gaskets, so just a thought for you, hope it helps.

  13. #13
    Member skip olsen's Avatar
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    Hi There Water Germlin give me a call and I'll tell you how to solve that problem 907-322-3291

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    Quote Originally Posted by Rutting Moose View Post
    If you have oil blowing out of your dip stick I would think it would not be your gauge.
    I have a mechanical oil gauge if you want to try it.
    True, I missed that part.
    My bad.
    Tennessee

  15. #15
    Moderator LuJon's Avatar
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    I am still a fan of the leak down tester and a good stethescope for diagnosing valves,head gaskets, and rings.
    After breaking off a head bolt below the deck line on a 4.3L before even reaching tourque specs I vowed to never use anything but ARP bolts for rebuilds. The 12pt bolts are monsters and following the ARP specs you get a race proven seal.

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