The Stovebolt Site Forums The Shop Area Engine Shop oil diluted with gas

Hi
I just bought my 1938 chevy 11/2 ton truck with a 216 engine. I changed the oil
but the level went up after I started it up a few times and ran it a short distance
I drained the oil and its gone real thin and smells like its got gas in it!
Any ideas?

There is a good chance the fuel pump is leaking into the engine. If so, change it immediately because it will squirt gas on the cam and ruin the cam in no time.

What he said. Don't dally.

Also another hazard (time for a story).In winter of 1958 school in our small town let us loose for thanksgiving and a friend whose father traded cars had let him have a 38 chevy pickup he had taken in trade and was too rough to resell so he chopped the body off and was having a fine time driving it around in the field behind the house.After several hours of this the engine quit and friend proceeded to remove the dist cap to check the points.When he flipped the points open with a screwdriver creating a spark the crankcase vapors exploded with a thunderous roar.Boys ran in all directions and when the smoke cleared they reassembled to view the damage which was only valve cover and side cover gaskets protruding everywhere, the crankcase breather was found quite a distance away,and the dipstick was out of its tube but just a little work and a new fuel pump to keep the gas out of the pan and she was back on the go.
That was the first but not the last crancase explosion in our little circle a later one on a flathead plymouth sent a man to get some stitches in head where he was hit by the oil filler/breather cap.

Would the fuel level in the carb float chamber cause gas to get into the slightly worn bores then into the oil?

For peace of mind,I would rebuild the carb,buy a new fuel pump.

Doing the above is cheaper than rebuilding or replacing the engine.

Adam, not knowing what carb you have I must speak in general.If fuel can make it from the bowl into the throat of the carb some will evaporate and the rest will pass into the manifold/cylinders/crankcase.When this condition exists you would be experiencing hard restart when warm/hot and the idle would probably be bad and fuel would be seen dripping into the throat of the carb at idle or after shutdown.If you could stand to keep an engine working in this condition the crankcase would likely see a slow rise in level but if it were worked hard most of the fuel would boil off and be vented to atmosphere.Most carbs are designed so fuel cannot transfer by gravity from the bowl without unusual circumstances-one exception is the quadrajet and it's derivitives.The fuel pump is your most likely cause and this is a common failure.The pump most times has a telltale hole in the body under the diaphragm near the mounting flange to indicate leakage.The hole could be plugged w/grease and dirt and I have seen some pumps without the hole.