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What caused fuel to get in my oil? Could this have caused the engine to blow up?

Old 07-29-2002, 06:53 PM
Uncle Toys
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Default What caused fuel to get in my oil? Could this have caused the engine to blow up?

I am still trying to understand why after two weeks and 29 hours with a super charger, one of my engines blew up. Two weeks after the incident, we dropped in a new engine and took it on the lake for a water test. A couple of minutes out I notice the oil pressure on the old engine (port side) was about half normal. Upon checking the dipstick, we found fuel in the oil. Limped back, changed the oil and took the Whipple supercharger off. Now I am back to stock 6.2s.

The mechanic told me if I had continued running the engine it probably would have blown just like the starboard engine had. Probably would have seized a bearing.

Dustin and I just discussed this on the phone and he believes the fuel could get in the oil by: over rich, detonation, or bad rings. Its hard for me to believe its bad rings on both engines after only six month and 71 hours total time. Detonation, I dont know? Over rich Dustin feels it would have shown on the spark plugs or my transom.

Up until this event, the consensus had been I ran the engine out of oil. I thought that was far fetched, but didnt any evidence or the technical ability to debate it. In a weird way I am glad to find the fuel in the oil and get me of the hook for not putting oil in the engine.

What do you guys think? Help me understand!
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Old 07-29-2002, 06:55 PM
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That sucks UT. Just the kind of worry I have about putting Whipples on my Hp500EFI's.

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Old 07-29-2002, 07:02 PM
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Default How about the intakes?

A bad seal on the intakes might force fuel into the crankcase...
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Old 07-29-2002, 07:12 PM
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If the fuel is washing throught the cylinders and getting in the oil it will cause a problem. I am having a rich condition issue right now with mine. My plugs are black and the treads have gas on them. The motors run good but will load up, I get black smoke when comming down from plain at about 2000 rpm, long idles, flooding at start up, and hesitation when hitting rough water or big waves at speed, but I do not have fuel in the oil. I do not know how the fuel could be getting in your oil but it will dilute the oil enough to cause damage. Good luck
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Old 07-29-2002, 07:21 PM
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A non-blower motor will have a larger piston/cylinder gap than what would be ideal for a blower motor. Pressurized fuel going into a cylinder, with a generous piston clearance, could force fuel pass the rings

That must be a pisser ... good luck with getting it squared away.


Last edited by cigarette1; 07-29-2002 at 07:54 PM.
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Old 07-29-2002, 08:18 PM
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CIG1 I think that his blocks were stock and he just added the whipples. I am amazed that this had Dustin stumped He from what I hear does not sell things until they are really tested. I am sorry to hear about your problems.

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Old 07-29-2002, 08:40 PM
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When Tyler re-worked my engines he put different rings on because of the blower application. So far no gas in oil after about 25 Hours on each engine. One I am losing a little oil because of a small leak. I check the oil Every Time out just to look for "too much oil" thus indicating fuel in the oil. So far so good for me. I would call a Big name engine builder and discuss their experiences.
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Old 07-29-2002, 08:50 PM
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When you checked your oil could you smell the gas?? Detonation - no way,

Over rich, yes, but I agree with Dustin about if over rich it should up on the transom or spark plugs. Were plug checks coming out perfect every time, & I am assuming transom has shown no signs of getting black.

Bad rings, possible but both motors to have this problem & being fairly new, I don't know. If the rings were bad that would be showing up by too much blow-by (blowing oil out the breathers or dip sticks.)

With the one motor torn down that you blew, What do the pistons, & cyld. walls look like? Got any pictures?, maybe they will give us an idea.

Ok, I have to ask, Do you ever check the oil??
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Old 07-29-2002, 08:50 PM
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Is is a carb motor or EFI? If it is carbed, I would check in to your fuel. Had a B class raceboat and one race prior to the start motor just quit and then hydralic'd. Pulled plugs and found fuel. Ended up being dirt clogging the jets. Drained fuel, cleaned jets, never had a problem again. Hope that helps.
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Old 07-29-2002, 08:58 PM
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ive had electric fuel pumps and a sticking needle valve in the carb fill a crank case full of fuel. if you have electric fuel pumps without percautions or even if wired to you ignition you leave the key on to listen to music wouldnt take long.
just a thought
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