454 Big Block 7.4L Gasoline in Oil

man-of-war

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Hello,<br />I finally got my boat in the water after having the lower portion of my engine rebuilt and last weekend I replaced the oil and filter and went out on the lake to try different prop sizes. On Sunday I checked my oil level and it was 2-3mm above the oil level mark on the dipstick and the oil had a gasoline smell. I changed the oil and filter and removed the four barrel Holly. While holding the carborator in the palm of my hand and moving it from side to side (no more than a 20 degree angle from side to side) it leaked gas into my hand. Is this normal? Are the plug gaps supposed to be .32? Would having gas in the engine oil harm the engine? Thanks!
 

Don S

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Re: 454 Big Block 7.4L Gasoline in Oil

You probably have a defective fuel pump, if your particular 454 has a mechanical fuel pump mounted to the block.<br />Yes gas will harm the engine, it dilutes the oil and it's no longer a lubricant.<br />The plug gap depends on the year, and model (Merc, Volvo, Other) 454 you have. Just like cars, they change over the years.
 

man-of-war

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Re: 454 Big Block 7.4L Gasoline in Oil

Don S,<br /><br />Thanks for the reply. This engine is a 7.4L 454 1975 GM Model. Today I replaced the four barrel Holly with the edelbrock 1410-750CFM as well as a new High Performance Carter Fuel Pump. I replaced all the fuel lines and fuel filter, the oil and oil filter (again). While tuning the carborator today, I ran the engine for about 15-20 minutes in the driveway, the fuel pressure gauge was reading 6psi and pulsing. After 10 minutes of idling it slowly went down to 3.5psi and still pulsing. I checked the oil level after I was done tuning the carb and it had the gas smell again. Any suggestions would be appreciated. Thanks!
 

Don S

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Re: 454 Big Block 7.4L Gasoline in Oil

Was that a "Marine" fuel pump and carburator you used? Automotive is a NO-NO on boats.
 

man-of-war

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Re: 454 Big Block 7.4L Gasoline in Oil

Hi Don,<br />Yes the carb is a marine one and the fuel pump was matched to what was on the engine by the mechanic that rebuilt the engine. I don't think that the fuel pump is the part that is causing the problem as the one that I replaced was working fine last year. What else can be causing the fuel to mix with the oil? Thank you.
 

waterone1@aol.com

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Re: 454 Big Block 7.4L Gasoline in Oil

After you shut off the engine, if you look down the throat of the carb, do you see any gas dropping onto the throttle plates ? Second thought : assuming that engine has a clear tube running from the fuel pump to the carb base or manifold (safety line for fuel pump), do you see any sign of fuel in that hose ? Third thought : are you sure it is firing on all eight cylinders ?
 

man-of-war

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Re: 454 Big Block 7.4L Gasoline in Oil

Hi Waterone1,<br />This fuel pump doesn't have a safety line on it. How would the gas get into the oil pan? How do I perform that cyclinder test? Thanks!
 

Don S

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Re: 454 Big Block 7.4L Gasoline in Oil

A marine fuel pump will have a hose barb on the pump for a small hose going to the carb. That hose prevents fuel from going into the bilge if the fuel pump fails. If you don't have that, or a way to put a fitting there, and have a weep hole in the pump, then it's automotive.<br />As far as what else would cause that much of a leak, I have no idea. If it was a carb running rich the fuel would go out the exhaust. If it was dripping into the intake, it would go into the cylinders and have to leak by the rings, and I don't see that happening in the quantity you have and you are getting the gas in the oil while running.<br />I've also seen enough of the So Called "marine mechanics" out there that really aren't marine mechanics to know that MATCHING a fuel pump sounds like he doesn't know what to look for.
 

man-of-war

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Re: 454 Big Block 7.4L Gasoline in Oil

The mechanic already got paid. i know its mean to say but i just cant help but think that he threw a wrench in the engine to cause this .after i check to see if all cylinders are fireing ,ill do a compression test, around what psi should i expect? If all goes well what test could i do to test the intake manifold for a crack ?all the plugs are wet with gas could this be decause of the .32 gap?????? thanks
 

Don S

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Re: 454 Big Block 7.4L Gasoline in Oil

all the plugs are wet with gas
Any other tidbits of information you would care to share before going into this anymore? Does the choke work properly? Has the engine been tuned up so it can burn the fuel?<br />If you are going to do a compression test, do it properly.<br /><br /> Compression Test HowTo
 

waterone1@aol.com

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Re: 454 Big Block 7.4L Gasoline in Oil

Oh Boy ! So far, this is what I am getting here: engine that has recently been rebuilt by someone that is questionable, engine (rings) not broken in yet, automotive carb and fuel pump, wet (with gas) spark plugs, and someone "throwing parts at it" like there is no tomorrow. Ok, to start at the begining. There is only one way for gas to get to the engine, that is through the carb. Second, there are only two ways for gas to get in the oil, either through the cylinders and past the rings, or directly from the intake manifold past the gasket to the oil gallery. Since we have wet spark plugs, I have to think that the gas is getting into the oil through the cylinders and past the piston rings ( gas is soo much thinner than motor oil). We know that this engine runs, and since I haven't heard that there are big clouds of black smoke behind the boat ( haven't left that detail out....have you). The only conclusion I can come to is that the gas is entering after the engine is shut down (way too high of fuel pressure or screwed up carb) or it is entering through one or more cylinders not firing and leaking past the rings.
 

man-of-war

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Re: 454 Big Block 7.4L Gasoline in Oil

this engine has been tuned to 16 degrees advanse, it runs and starts well,the holley 4 berrel had no choke . the ebelbrock 1410 marine carb has an electric chike,after the engine is switched off this choke remains open for about 8 min . no smoke when engine is runing.but haveing to much fuel pressor sounds right .after installing the new carb i installed a fuel pressor gague the reading was 1 notch past 6 psi and the nedel on the gague is pulsing, after about 15 min fuel pressor begins to drop and stays at 3 psi after 25min of idleing.
 

Olds Eddie

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Re: 454 Big Block 7.4L Gasoline in Oil

My guess would be float level too high, or bad diaphram in new fuel pump. I was service mgr. at a large auto dealership for many years and we replaced bad parts with brand new parts that were defective too often. The manufactures will replace parts but not pay for all the head sctatching it took to figure out the new parts were bad. Get a marine pump and carb on there before you blow your boat up.
 

man-of-war

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Re: 454 Big Block 7.4L Gasoline in Oil

Thanks for all the replies! <br />There is a marine carb on the engine, the only thing that is non-marine is the fuel pump which I will change on Monday. I checked the oil level today and noticed the new oil was a cream coffee colour which means there was water getting into the engine (condensation from using cold water to run the boat). I had the "monkey" mechanic come over to my house today to fix the problem. We drained the milky oil and hooked up a pressure hose to the rocker cover to force all the milky gas/oil out. We then poured in some fresh oil (10W30) and ran the engine for 10 minutes. The trick was not to turn the hose on full blast/not too use too much water pressure. By using too much water pressure the engine will never get to normal operating temperature (I live in Canada and the water is really cold...). The mechanic said that this is why the gas was getting into the oil. The new oil still has a gas smell to it but that is because of the old oil that couldn't be drained from the engine. The oil the mechanic recommended after the engine was rebuilt was 20W50 and my fuel pressure was always high at 6.5 psi and pulsing. Using 10W30 oil, the fuel pressure is down to 3.5 psi and holding steady-not pulsing as it did with the 20W50. I don't know if what I am saying makes sense but the engine is running fine now.<br />Thanks for all your help!
 
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