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Old 12-10-2004, 10:00 AM
cub cub is offline
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Gas in oil, Again!!

I have a 400 sbc. I had gas in the oil thought it might be the carb so I bought a new Holley 750 with vac sec. Changed oil crank it a few times and now I have gasl in the oil again. Any ideas what might be causing this?? Thanks, Randy

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Old 12-10-2004, 12:25 PM
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H'mmm

How is the fuel pump? could it be a leak through the back side of the pump allowing gas to get into the oil pan..??

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Old 12-10-2004, 06:40 PM
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Electric fuel pump with 5 psi of pressure.
So I have no idea, someone told me it might be a cracked intake.
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Old 12-10-2004, 10:07 PM
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What did you mean when you said you cranked it "a few times" ? If you meant turning the engine over a half dozen times then you have a whopping problem.

With the fuel pump excluded, that leaves the carb and intake. If the carb isn't dumping gas, that leaves...
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Old 12-11-2004, 12:47 PM
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MI2600, This car is still a project car so I cranked it a few times and pulled it in and out of the garage. It is not driven on the street yet. so it has not been run maybe 30 min total. This is why I wanted some opinions, it is is not like I drove on a 2 hr trip and had gas in the oil so I don't know what is going on. As I said the carb is new
and I can not see it dumping gas. Any Ideas???
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Old 12-11-2004, 12:55 PM
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Well, there's only a couple ways gas can get in the oil...past the piston rings or into the lifter valley.

I'd first check the plugs to see if they're all wet with gas. If not, then it's time to pop the intake and look for faulty gaskets or cracks/holes.
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Old 12-16-2004, 07:31 PM
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I'm wondeirng if your rings are stuck from lack of use and the gunk that has turned to varnish is locking them up. With a rich mixture it would be easy for fuel to just "wash" down the cylinders. Usually the crank case pressures will keep anything from entering the block through a cracked or missaligned intake manifold gasket. It typically goes the other way....oil into the intake tract. Hmmmm....on deeper thought I wonder if you have a cracked ring. Do a compression test and you will know real fast if the fuel is washing passed the pistons.
Last thought, a blown head gasket could allow cylinder gases to enter the crank case. I have personally had blown head gaskets leak into everything...coolent into the oil, oil into the coolent, gases into the crank case...just depends on the path of the leak.
I would think a leak down tester (pump up the cylinders and listen for where the "hiss" is) would pinpoint the crank case leak.
Good luck!
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Old 12-18-2004, 09:18 AM
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Not to sound ignorant but how do you know there is gas in the oil? Thin, smell, or how are you telling? Also have you pulled the ntake back off to double check for cracks, or bad intake gasket? How many times or how long are you cranking it at times?

Kevin
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Old 12-18-2004, 03:14 PM
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Well I checked the compression and it has 215psi pretty much even on all cylinders.
I can tell I have gas in the oil by pulling the dip stick and I see gas on top of the oil and you can smell it. Thanks for the replies and help.
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Old 12-18-2004, 05:30 PM
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I can tell I have gas in the oil by pulling the dip stick and I see gas on top of the oil and you can smell it
I don't think you will see gas "on top" of the oil as the gas would dilute the oil down and both will mix together especially when mixing while cranking the engine.
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Old 12-18-2004, 10:22 PM
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Have you got a fuel pressure regulator? If not you need one as those electric pumps will push the needle off the seat in most carbs. It has happened to me with a new 750 Holley on a 350 SBC so I'd give that a try.
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Old 12-19-2004, 10:14 AM
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I have fuel pressure regulator set at 5 psi, I would say that is not too high. As for the oil and gas mixing in the crank case I',m sure it does but I may not crank the car for 4 or 5 weeks and the oil and gas seperate.( at least I think so) Thanks for all the replies. Randy
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Old 12-19-2004, 10:27 AM
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Following the thread

I have been watching this thread and it is possible that there is water condensation in the crankcase..in normal use this gets boiled off from the heat of the oil and the engine..setting for long periods allows the condensation to build up and seperate so we see what we see..

As far as the gas odor..well that can happen if there is the type of venting arrangement (PCV valve) that allows gas vapor to get to the crancase..

I have seen water in oil specially in RV applications where the vehicle is seldom driven or in wrecking yard motors tha thave set for a long time..

Bout the only way to really tell is to send out an oil sample to a testing lab to see what is really in the oil..

OMT
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