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Hot Rods gas in the oil!!!

Discussion in 'The Hokey Ass Message Board' started by southern thunder, Apr 16, 2016.

  1. southern thunder
    Joined: Mar 14, 2012
    Posts: 226

    southern thunder

    Hey Guys, I was on a few months ago with problems with a 350 chevy in a pickup. It was backfiring, no power, hard to crank, after it ran for a while it wouldn't crank at all. Well, over the months, I set the timing correctly, installed a new 1850 holley carb. adjusted the lifters, all the possible problems everyone touched on. one thing made it better, the next made it worse. it has never been right since it was over revved while working on it when I first got it. I even pulled out the pushrods to see if one was bent, nothing seemed to be out of order in a manner of saying. Now I pulled the cam out, looked ok, timing chain and gears looked good. I had a new cam in the box from another project I didn't use, so I put it in this engine. been just working on it little at a time, when I had some extra time, etc. and also installed a highrise manifold i had laying around. I had got a little water in the lifter valley when I did all this, and today changed the oil to put fresh oil in and a bottle of the zinc additive. when I pulled out the drain plug a strong smell of gas was in the oil. and the viscosity was about that of 3 in 1 machine oil, not even probably 5 weight. My question is, How can gas get into the oil like that? this was alot of gas, filled a 2 gal. bucket up 3/4 full. when I change oil it usually fills it to half or there about. Any ideas on this ?? have I got big problems somewhere??? thanks.
  2. Zerk
    Joined: May 26, 2005
    Posts: 1,418


    While a lot of cold starts and short trips will do that, it could also be a bad fuel pump diaphragm. And that's also something that can give you running problems.
    OLSKOOL32 likes this.
  3. Pete Eastwood
    Joined: Jul 27, 2011
    Posts: 1,166

    Pete Eastwood
    from california

    If it has a mechanical fuel it could be a bad diaphragm, that will put fuel in the pan.
    vintage44 and OLSKOOL32 like this.
  4. midroad
    Joined: Mar 8, 2013
    Posts: 296


    Do you have a mechanical fuel pump? If you do, does it have a ruptured diaphragm leaking into the sump?

  5. roundvalley
    Joined: Apr 10, 2005
    Posts: 1,774


    Pull the air cleaner and see if it drips gas in the carburator after you shut it off.
  6. southern thunder
    Joined: Mar 14, 2012
    Posts: 226

    southern thunder

    it has a new mechanical fuel pump ( that doesn't mean its not bad) how can I check to see if the fuel pump is bad? as far as the carb. I will check that. Thanks guys.
  7. Could the gas been in the oil before you changed pumps, if you couldn't run the engine long it would not get hot enough to boil it out ??
  8. southern thunder
    Joined: Mar 14, 2012
    Posts: 226

    southern thunder

    since I have had the truck it hasn't run over 15-20 min at one time. The fuel pump that was on the engine when I got the truck went bad just after I got it. the truck had sat up for couple of years when I got it. The gas could have gotten in the pan then, as the pump was going bad and I didn't know it.
  9. oldcars.acadia
    Joined: Jan 20, 2003
    Posts: 213


    Gas in the oil. Depending on the truck, Is the fuel tank above the fuel pump level (cab tank)? If the pump fails it is possible for the base to fill with gas when the truck is stored (not running). Rough running after over rev. Have you checked compression? May have bent some valves.
  10. frosty-49
    Joined: Oct 13, 2014
    Posts: 118


    Have an electric fuel pump pushing through the mechanical? If so get rid of one.
  11. Engine man
    Joined: Jan 30, 2011
    Posts: 3,480

    Engine man
    from Wisconsin

    Gas in the oil will wipe a cam in a short time. If the engine sat for a long time, any open valves can rust on both the valve and valve seat causing poor sealing of the valves. Does it run better since the oil change? Have you drained the fuel tank. If it sat,any fuel in it is likely bad
  12. Blues4U
    Joined: Oct 1, 2015
    Posts: 6,735

    from So Cal

    2 Gal's of oil drained from a 1 gal pan is a lot of gas. That much gas is likely from a failed mechanical fuel pump. I don't think a lot of short trips could result in that kind of fuel dilution. If it was dripping from the carb after the engine was shut down, that much gas would likely result in hydro-lock when trying to start it. The most likely cause is a failed diaphragm in a mechanical fuel pump.
    OLSKOOL32 likes this.
  13. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 29,150

    Jalopy Joker

    Holley carbs sometimes known for flooding over when a float sticks or sinks or debris contaminates the needle & seat from fully sealing closed & shutting off fuel flow when float bowl is full
    DdoubleD likes this.
  14. gas & guns
    Joined: Feb 6, 2014
    Posts: 370

    gas & guns

    Mechanical pumps are cheap. Probably less than an oil change.
    Bolt one on, change oil, and I would bet it cures the problem.
  15. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,695

    Member Emeritus

    When I first started getting into cars, 1967 or so, with my 56 Chevrolet with a 265 V-8/Powerglide, I noticed these two little holes on either side of the fuel pump were leaking gas (???). I promptly stuck a couple of small sheet metal screws in them, and stopped the leaks. Then I noticed my crankcase oil was "increasing", and smelled of gas. Guys I worked with at the Standard Chevron Dealer told me to replace the fuel pump, and change the oil. Sometimes we learn the hard way. Seems the fuel pumps don't last as long now with the alcohol in gas either. I am Butch/56sedandelivery.
  16. I agree with Butch.My rubber fuel lines in my station wagons and lawn mowers don't seem to last long with this new gas.Bruce.

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