Gas getting into Oil

[Ivy Vimba]

Installed a rebuilt 350 GM engine with a 4bbl carb. Ran the recommended 10 hours break-in period. Changed the oil, and got out 6Qt of thin, black oil when I only put in 5Qts.<br />Assumed a fuel pump(external, electric) and/or carb problem so installed a rebuilt carb and put an adjustable pressure regulator on the gas line set at the recommended 4psi. Ran the boat another 10 hrs, changed the oil with similar results!<br />I need to resolve this before the boat blows up!!!! <br />BTW, the boat & motor runs fine.<br />Any ideas on possible causes???

 

[Toontime]

Re: Gas getting into Oil

Based on the plethora of replies, it looks like everyone is as puzzled as I am. I'm no mercaholic but I've wrenched a chevy a few times and the only way I can see your problem happening is for gas to be leaking thru the intake into the valley pan and crankcase. Might even be pulling vacuum in the crankcase if the relief valve is stuck or obstructed. If that's the case and the intake has no cracks, new intake gaskets or pvc valve/ vented oil fill cap would cure it. The gas will evaporate out of the oil eventually.

 

[Flip South Dakota]

Re: Gas getting into Oil

Couple things to check. One is a stuck choke but I don't think that's it because the engine would just die out when you opened the throttle. Another thing is you may be way over propped. You could be dumping a bunch of gas into the engine but she's not burning it off and it's getting into the oil.<br /><br />Also you might want to look at your fuel pump they sometimes go goofy and start dumping gas into your oil if a seal goes bad. That would be if your running a carbed engine with the old style fuel pump.<br /><br />Once the gas gets into the oil it's there for ever. It will not evaporate off, it just thins out your oil and you start to lose lubrication. NOT GOOD.

 

[Easttxhunter]

Re: Gas getting into Oil

I would double check the fuel pressure. Make sure it is 4psi or less. It sounds like to much fuel pressure to me. I have an old 8n ford tractor that is gravity fed. Sometimes going up a hill it would die. So i put on the smallest electric fuel pump i could find 2 psi Well that was way to much Had gas in the oil like yours. Had to go back to orignal setup Anyways hope that helps Good Luck.

 

[Easttxhunter]

Re: Gas getting into Oil

Forgot to tell you that the pessurre was to much and the float could not overcome the fuel pressure to shut off the fuel So the fuel just get getting dumped in what was not burn off ended up in the crankcase