Fuel in engine oil

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scott hoffman

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Hi this is Scott, I am trying to trouble shoot some problems on my Father and suns project 1972 360 Duster. I am trying to tackle a little at a time as this will be for my younger sun and he has 5 years till he could legally drive this car anyhow. The car is a 360, 727 83/4 391 gear Duster. When I first got it she had been sitting for 4 or 5 years and there was a strong smell go gas coming from the oil. I changed the Carb from the tired old holly to a new Edelbrock, then I changed the oil. Ok so I have not put any milage on the new 360 other than running it to worm it up in the garage for the last 6 months and today i pulled the dipstick and there it is again gas in the oil. I do not want to run the motor again till i know why this s going on, and how to fix it. I am sure a lot of you guys have forgotten more then I know but man this duster is making me learn. Thanks for any assistance.
 

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excessive fuel pressure? How much gas, a bunch or does oil just smell ? Starting with choke then shutting down without driving could potentially fuel foul the oil but wont raise it 1 qt over on stick unless carb is flooding due to excessive pressure or bad seats
 
Either / both the above. Bad fuel pump is no joke. I've been party to TWO passenger car crankcase explosions caused by fuel dilution.

Carb way too rich and or leaking fuel past the needles.
 
I agree with hangnOut in post #2
The mechanical fuel pump has a diaphragm in it that has gas sitting on it almost all the time. So long as the fuel level in the tank is higher than the pump, there will be fuel in the pump. If the diaphragm has a perforation in it, the gas can find it's way into the crankcase pretty easily. The fuel in the line between the carb and the pump can also drain back through the pump, although the checkvalve ought to prevent that. If the Edelbrock bowls go dry in a very short period of time, it might also be a bad carb, as in a cracked mainbody, although that would be highly unlikely.
The pump is easy to prove
 
it's not a lot but the oil just smells, Ive never had this happen on my 340 roadrunner. The carb is a fresh rebuild, and is the second carb on the motor in about a 12 months.
 
the fuel pump is relatively cheep is there any trick to changing it or is it just straight forward? Thanks guys
 
Bad fuel pump; you have a new carb and haven't really run the car so that pretty much narrows it down to the pump.
 
If the pump seems to be all crossed up, turn the engine over by hand, until the pump-drive rotates away from the arm, and it will go in straighter.
Bub a little moly on the arm where it contacts the eccentric drive.
 
I spun a bearing in an engine because the carb was way to rich and the timing was to low,not burning the fuel.It also actually raised the oil level.It did not take it long to ruin the engine
 
After replacing the fuel pump I would not attach to the line from the tank. I would use a 5 gallon gas can and attach using a length of fuel line directly to the input of fuel pump and then start the motor. Run it for 10-15 minutes and allow it to reach operating temperature. Watch oil pressure and temperature gauges. Be sure there is adequate ventilation!! Old gas or gas left in a tank for along time even with fuel perservative may give off a smell in the oil. Good luck
 
I would also verify fuel pressure.
I have a couple of Eddy's and they are very sensitive to fuel pressure overload.
My regulator is set at 5.5 psi which is what Eddy states.
My Mechanical Holly pump puts out 7.8 if I open the regulator all the way. Floods out in a hurry.
 
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