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Thread: Gas in Oil?

  1. #1
    Join Date
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    Default Gas in Oil?

    My question is, does "gas in oil" look just like "water in oil"? I've been breaking in the recently rebuilt 455 in my Cutlass. After I had let it run for a while the other day, my dad told me to cut it off and check my fluids. My oil was milky colored like water was in it. I had no leaks anywhere, so I drained it all out and noticed it smelled like gas. So after it had all ran out, I changed the filter and refilled it w/new oil. After letting the car run for a while, I cut it off and checked the oil again. It was the same way again. What do you think it may be, water or gas mixing w/the oil? And what may be causing this?

  2. #2
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    Default Re: Gas in Oil?

    Well, there are only a couple of places raw fuel can enter the crankcase. The most common is a leaking carb that dumps enough raw fuel into the intake to wash down past the rings. The other is a bad fuel pump that leaks internally and dumps fuel into the crankase. Are you running a stock fuel pump, or an aftermarket pump system with a pressure regulator? By chance is there enough fuel pressure to keep the inlet needle from closing against the seat? That could force the fuel to overfill the bowl and dump out the vents, creating an over-rich condition that could foul the plugs and let raw fuel flow past the rings, contaminate the oil, and possibly damaging the cylinder walls, rings, and pistons.
    If you are running a Q-Jet carb, they are notorious for leaking internally at the soft plugs under the main body. If they are leaking, you will notice it takes longer to start the car after it has been setting awhile because the fuel bowl will have to be filled up again before it will start. You will also smell gas fumes under the hood.
    If the pump is leaking into the crankase (a somewhat rare event, since most pumps have vent holes that let the gas drip out if it is leaking) you have a dangerous problem that could cost you an engine or even your car. Once you change the oil, keep a record of the oil level and check it very soon after you shut off the engine (within 5 minutes). If the fuel pump is leaking into the engine the fuel will increase the oil level enough to notice it on the dipstick after a short drive. Either way, you risk serious damage to the motor driving the car in it's current condition. I would check the carb and the pump as soon as possible before a fire or an explosion ruins your entire day.
    Good luck, Randy
    Randy & Kelley Sprague
    67 Riviera
    98 Riviera SC-SOLD to my daughter
    02 Silverado LS

    "Fast is only fun if you can do it more than once without dying in the process"

  3. #3
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    Default Re: Gas in Oil?

    Alright, thanks for the info.
    I'm currently running the *original* stock fuel pump and a Q-Jet from an Olds 307. I'm looking at upgrading to a Summit 750 Carb and Summit electric fuel pump w/fuel pressure regulator when I come home from Basic Training. I'm gonna check on what you said tomorrow and see what happens. Also, would the PCV valve possibly have anything to do with it?

  4. #4
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    Default Re: Gas in Oil?

    The PCV lets the engine vacuum pull the vapors out of the crankase so they can be burned internally with the fuel/air mixture instead of venting out into the air. If it stops working in a closed position, you may notice some new oil leaks when pressure builds up inside the engine, and eventually has to get out somewhere. Sometimes it flows back through the vent line that runs between the valve cover and the air breather, oiling up the inside of the air cleaner. If the PCV sticks open, it will act like a vacuum leak at low rpm and potentially lean out the fuel mixture while the engine is at idle. The danger comes when you have a PCV that is stuck open, a crankcase full of oil and gas, and the engine backfires. The operative word here is BOOM. Fortunately it doesn't happen very often. It is cheap insurance to replace the PCV, but I think you have a different problem. Hopefully it is something simple like a leaky carb.
    Have you re-jetted the 307 carb to get it to feed the correct fuel/air ratio to the 455? I would think the jetting would be alot different between the 307 and 455 carbs, although I have no way to verify that. Your 455 needs considerably more air volume than the 307 did. Later, Randy
    Randy & Kelley Sprague
    67 Riviera
    98 Riviera SC-SOLD to my daughter
    02 Silverado LS

    "Fast is only fun if you can do it more than once without dying in the process"

  5. #5
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    Default Re: Gas in Oil?

    what are you calling "milky"? is the oil overfull and looks like a coffee frappe on the dipstick or just some residue under the oil cap? if it is the first you have water getting in the crank case. which is bad. if it is just some build up under the cap then that is condensation.
    paul c.
    65 skylark conv. 455/th400
    79 z28 w/a dart block and headed 555 bbc. hopefully 9.50
    2 jetskis
    mountain bikes and road bikes
    no more hobbies please

  6. #6
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    Default Re: Gas in Oil?

    Sounds like a cracked block.
    Yardley
    2008 BPG Nationals BCO Race Champion
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    1969 Riviera GS Stage1 Clone 12.92@106MPH!!!!

  7. #7
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    Default Re: Gas in Oil?

    Just to prove or disprove the broken block theory, are you losing any anti-freeze out of the cooling system that isn't leaking out on the ground? Water mixed into the oil will make it smell funny, but I don't believe it smells anything like gas. Keep us posted on your progress. Later, Randy
    Randy & Kelley Sprague
    67 Riviera
    98 Riviera SC-SOLD to my daughter
    02 Silverado LS

    "Fast is only fun if you can do it more than once without dying in the process"

  8. #8
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    Default Re: Gas in Oil?

    Alright, I've replaced every gasket on the top end and the leak has decreased significantly. It was water getting into the oil, its still leaking somewhere on the passenger side. The carb is operating correctly(I'm still changing it). No, the block isn't cracked(I have another 455 block that is) and my heads are fine. My uncle told me to use my original intake instead of the Edelbrock intake and that should solve my problem. I'm gonna try that tomorrow and hope for the best.
    '83 Cutlass w/'70 Buick 455 on 26"s


  9. #9
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    Default Re: Gas in Oil?

    Do you use any sealant with your intake manifold gasket?
    If so, where and what kind.
    Do you use a torque procedure when installing an intake manifold?


    ElectraJim
    I won nothing at the '09 GS Nationals..except a ZR-1 smackdown
    Yes, I raced at PINKS! All-Out in June 27-28 '08 Gateway International Raceway
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  10. #10
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    Wausau, Wi
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    Default Re: Gas in Oil?

    Could also be a head gasket leaking antifreeze into motor. I'd run a compression check to see if your loosing pressure anywhere.
    1968 Skylark, 455/TH400, KB CoolRunner Intake, Torque Tech SP235 cam, NOS PowerShot adjustable level plate system. Next I need a big honk'n carb

  11. #11
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    Default Re: Gas in Oil?

    I had this problem a few years ago with a small block Plymouth Cuda.
    "NO" the oil will not look like it has water in it ( milky white color). It will still look like oil ( pretty much normal looking) but will be "thin" depending on how much gas it has in it.
    My problem resulted from a mechanical fuel pump diaphram that was busted.... and as it pumped gas to the carb, it was also pumping gas into the crankcase.
    Believe me... gas is not a lubricant! ha!
    good luck!

    And as a note... if there is gas in the oil you'll definately be able to smell it on your dipstick.
    Jim

  12. #12
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    Default Re: Gas in Oil?

    be careful but if the oil dipstick will light on fire quick n easy.......

  13. #13
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    Default Re: Gas in Oil?

    Quote Originally Posted by qdub24 View Post
    I'm looking at upgrading to a Summit 750 Carb
    That would NOT be an "upgrade".

  14. #14
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    Mar 2007
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    Columbus, GA
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    Default Re: Gas in Oil?

    I'm leaving for my Army basic training tomorrow so this will be last update for a while.

    I've been using the black rtv silicone on the intake gasket/valley pan as the instructions from Fel-Pro suggest. I've been torqueing everthing down according the specs from TA Performance. My dad does the pressure test everytime we put everything back together. However,I still have a leak that's visible through the driver's side cylinder head as a stream of water.

    Yesterday, when we were taking everything back apart, my dad broke one of the head bolts off in the block. So while I'm gone he's supposed to break the motor back down, get the bolt out of the block, and put it back together. Hopefully, it'll be done when I come back home. I'll let you guys know when I get back.

    And what's wrong with the Summit 750 carb? I'm building a street car, not a strip car.
    '83 Cutlass w/'70 Buick 455 on 26"s


  15. #15
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    Default Re: Gas in Oil?

    I still have a leak that's visible through the driver's side cylinder head as a stream of water.

    visible through the cylinder head?

    what are you looking at, exactly? can you post a picture?

  16. #16
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    Edmonton, Alberta, Canada
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    Default Re: Gas in Oil?

    I had the fuel pump diaphragm problem before. Luckily it didn't destroy my engine...
    1972 Skylark Custom 4 door sedan powered by '70 455

  17. #17
    Join Date
    May 2007
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    Default Re: Gas in Oil?

    What do the plugs look like??
    Kurt

    69 Skylark - street/strip

 

 

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