Gas in Oil?

Ricky B

Ricky B

Wiiide Open
Joined
Mar 20, 2005
Location
LKN - Tha Dirty Mo (Mooresville, NC)
My bro's 78 F100 randomly noticed that the oil was looking thin and kinda milky, drained it and it smells like there's alot of gas in the oil, how does that happen? We just put a brand new 650ish (something close to that) holley truck avenger on it a few months ago, b4 that it had a 600 cfm edlebrock. Its a 400 smallblock with a edlebrock performer intake manifold and long tubes.

Thanks
 
Off the top of my head… it could be a bunch of things. Id start by pulling the plugs and looking for the wet ones, followed by a compression test. Gas in the oil is indicative of a misfire
 
I'd say you've got too much carb on an engine that probably has worn rings/cylinder walls. You know, a carb kinda has to be the right size for your engine. Will the engine even pull 600CFM? I'm sure there is a way to calculate this out, but then you've got to think about how worn is the engine.
 
off the top of my head I would say diaphram gone in the fuel pump. If not that, carb is dumping fuel. float hung or needle valve not seating.
 
Off the top of my head… it could be a bunch of things. Id start by pulling the plugs and looking for the wet ones, followed by a compression test. Gas in the oil is indicative of a misfire
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Well the timing is off, but barely, we just havnt took a timing light to it since we redid all the top end stuff but its about where it was before. Would a small amount of being off with the timing dump that much fuel into the oil?

I'd say you've got too much carb on an engine that probably has worn rings/cylinder walls. You know, a carb kinda has to be the right size for your engine. Will the engine even pull 600CFM? I'm sure there is a way to calculate this out, but then you've got to think about how worn is the engine.
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I've always heard 350's and up you run 600 cfm carbs, and it did run just fine with the 600 eldlebrock, switched to the holley for the truck avengerness.

off the top of my head I would say diaphram gone in the fuel pump. If not that, carb is dumping fuel. float hung or needle valve not seating.
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Well its just running the electric feul pumps you can get from advance for cheap, its the same pump im running on my Z71 jeep ad it works fine there . . . .

The carb is brand new but maybe it is getting stuck, I guess I should take it apart next time I get a chance (thanksgiving maybe?) and look.
 
Milky Looking?
That usually indicates water in the oil. Oil and water don't mix, so you get the water suspended in the oil, causing the milky look.
Gas and oil will mix, both are petroleum products, but you get the smell.


Matt
 
Lizooki said:
Milky Looking?
That usually indicates water in the oil. Oil and water don't mix, so you get the water suspended in the oil, causing the milky look.
Gas and oil will mix, both are petroleum products, but you get the smell.
Matt
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Thats why I was confused at first cause I didn't see any milky oil, but it def thinned out the oil big time and smells like gas.
 
I went through this and learned some valuable lessons... But your instance is different being it's a new carb? That 400 can easily take on a correctly built 650 Avenger! Heck, even a 302 can run rich on 650 cfm's. I've driven back and forth to work for 12 years now with one if someone wants to fight about it. LOL :)

First off I learned how gas in the oil will kill the viscosity resulting in oil being too thin to lubricate bearings! If you don't get that gas out it's so easy to scar the crank and cylinder walls resulting in a rebuild! Or worse - an engine lock up.

First thing you do right off the bat is pull the carburetor. Then the oil drain plug and get that tainted oil out. Then pull the dizzy and pump that gas/oil out of the oiling system. (drill in reverse with correct attachment) Don't even think about hitting that starter until you do all the above and refill with new oil and reprime motor.
9 out of 10 times it's a carb issue. But a compression check would tell if rings are bad. It's good to know your motor with a comp check if you have any doubt about the motor. Be sure to squirt some oil in cylinder between tests if you have bad compression to confirm it's the rings. If good compression, then fall back on carb dumping too much gas. Could just be a bad carb from the factory? Anything's possible. I've bought a bad spark plug before so I question everything now...
What usually happens is that the carb dumps too much gas and doesn't have time to fully combust and the remaining fuel gets squeezed past the rings into the bottom end past the rings. Same effect as just having bad rings though so the compression test needs confirmed first.
I know that this is a serious issue until you figure out what the problem is dude! I'll be watching this post to see the outcome. I know this story all too well though. Been there done that! Wasted a motor one time. Good thing it was a shitty old motor to start with. And too bad I didn't know all this to start with. Lived and learned on this issue...
 
elec fuel pump on a carb? did you put a regulator on it because the elec is a higher psi.
 
Franklin said:
elec fuel pump on a carb? did you put a regulator on it because the elec is a higher psi.
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Good catch Franklin. Yea, PSI should be regulated to under 6 psi if not around 4 or 5 on a carbbed setup. Electrics usually throw about 30 psi if not regulated.
 
1) Id pull every plug to see if any are "washed out"
2) You need to get some gauge on how much fuel the carb is dumping. Im not a big fan of the TA carbs, but Ive only messed with 1, maybe I got a bad.
3) id check compression and leak down, (rings)
4) Id double check that fuel pump. I had one on my Mustang taht was supposed to flow 7psi, but for whatever reason as it got a lil older, actually started flowing closer to 19psi and caused fueling issues. I cant explain the why, just that it did.
 
Just use a mechanical pump... much simpler and more reliable. But agreed, I bet your pump is pushing too much pressure. It would be very simple to check with a vac/pressure gauge. After that, did you ever adjust the carb at all from the base settings?
 
x400 on the fuel pump.

the holley needle and seat are supposed to be able to hold to 7lbs of pressure. Its my experience that anything 6 or higher will push past the ndl/seat and overfill the fuel bowl and run out the vents into the manifold.
 
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