i have a 350 small block chevy. i drove the car about 40miles and my oil pan was full of gas. i thought it was the fuel pump, but i've replaced it twice, both times same results.

Is this carb, injected?

What is the fuel pressure?

I suspect the fuel is leaking past the piston rings due to flooding and/or
one more misfiring cylinders.

How much fuel is in the pan?

its a carb. i'm running an old set of heads. ive been told that i need to run a short thread plug,but i have a long thread spark plug now. could this be the misfiring issue? i'm not sure about fuel pressure because i do not have a gauge.
these heads that i'm running are small chamber heads, they create lots of compression. could this high compression be blowing the diaphram out of the mechanical fuel pump? should i just get an electric fuel pump and short thread plugs?

Do you mean projected nose, or heat range?

When the spark plug is seated and indexed, the threads should be flush with the
combustion chamber. If they are protruding in, or set back, it's the wrong plug.

Heat range and nose projection are different aspects of the plug.

What do you have in there now, and what is the gap?


If there is a misfire condition, the wrong plug or gap could cause this...yes.

That may be your problem, or faulty needle/seat valve, and/or faulty
float...or wrong power valve etc.

You really should find out what the pressure is, but you can start by
listing the carburetor type and the base settings.

Have you done a basic tune on the carb?

No, there is no relation between the two.

Not yet, let's see what's up with the current setup.

sorry for the time between post, i'm at work and i leave at 5.
not sure what you mean by nose or heat, but the plug isnt flush with the inside of the chamber.i believe its too far inside the chamber to make proper detanation. the carb is a simple little holley 600. aluminum intake. i had my bro do the tune on the carb, it runs a little rich but nothing too drastic.could the fuel be sitting on the piston and riding it to the bottom of the block? that is my bro's theory.
i'm going to change the plugs and oil this weekend. i'll also pick up a fuel pressure gauge.
i have auto lite standard plug for 350. the gap is 35. i called advance and ask for a plug for a 1967 327 impala and they recommend the plug with short thread.

Alos be careful running this engine with gas in the oil. You could possible wash out your rings if not careful.

yeah, i'm kinda freaked out about that. i'm not going to start the car up until i change the oil and plugs. this is the third time this has happened. i'm kinda desprate for a fix. i've considered changing the heads but i hate to do all of that work if the problem could be as simple as 20.00 set of plugs.

If you give me the part number and plug MFG, I can tell you the heat range
and nose projection.

As for the part of the plug that needs to be flush, I'm referring to the top
ring of the thread...not the electrode.

You don't want detonation my friend!

Too rich with a combination of bad ring seal possibly. You would have to
have poor atomization of the fuel and extreme misfire to have enough
raw hydrocarbons to pool up in the oil pan. This is far beyond a rich
condition.


Good plan.

Which Autolite plug? The gap may be a touch tight for the compression
and RPM of the motor. You could probably open that up 0.010" and still
be fine. That's something you can try with the fresh plugs.

Check the gap on all the plugs when you pull them out and post them.
Also take pictures of the electrode, and inside the core area if you can.

Post them up, and let's have a look.

could the fuel be sitting on the piston and riding it to the bottom of the block? Too rich with a combination of bad ring seal possibly.

Um piston better be sealed at the bottom of the cylinder too... lol
sounds like youve got bad rings to me....do a compression test on the motor and post your results, and a cylinder leakage test too if ya can...give that info and i can probably tell ya exactly whats wrong

i'll get pictures this weekend.
let me tell you a little about the engine so you'll know where i stand.it's in a 1986 irocz, it's the 010 casting, it's been decked 010, and it's bored 40. i put these heads on when the engine was freshly rebuilt,we rebuilt the heads in the garage.once i put them on the car, i could'nt rev it because the push rod hole was wallord out and the rocker arm would jump off and it would bend a push rod. at the time the car needed a lot of body work so it sat with less than 1600 miles on the engine. i had the heads reworked,shaved 7 thou, new valves, screw in stud,and guide plates.i originally had an electric fuel pump but i went with a machanical once i put the heads back on. i fixed the body work, pulled the engine out, painted it and the car under the hood and jams, put the engine back in, and now this.

wow, so u shaved the heads and decked the block did u have the intake milled? we just talked about this in my engines class today, it will look good at the top like the intake fits right but it will be leaking underneath into the lifter valley, that could be where your gas is coming from..

#1 candidate is the mechanical fuel pump.

#2 would be the fuel bowl well plugs on the bottom of the main body of a q-jet. You didn't say what type of carb you have, but Holley and Edelbrock type carbs don't do that. So, only possible if you have a q-jet.

Spark plug - non-credible. You might get some fuel into the oil with a completely misfiring cylinder, but you could certainly hear and feel that. And, if that was happening, running the engine with fuel in the oil would be the least of your problems, as the misfiring cylinder would be completely washed down, anyway.

Intake mismatch - non-credible. It is going to leak air and oil into the cylinder before anything else happens. Perhaps if #2 and a mismatch are true, but you'd be fouling spark plugs before the oil pan would be "full of gas".

If this is the third time this has happened (3rd fuel pump, you said), and you didn't change the oil each time it happened, shame on you (couldn't tell from what you said).

Do you have the PCV system set up properly?

how would the mechanical fuel pump get gas in the oil pan?

If the diaphragm that pumps the fuel leaks internally, it goes directly to the oil drain-back.

i have a small holley.
i did change the oil every time. is there a possibility that the high copression is blowing the diaphragm out of the fuel pump?
when i picked the block up from the machine shop,he didnt have the fuel pump rod(not sure what you call it) the guy had to look around and he found one laying on his shelf. are there different size pump rods? could i have the wrong one? will this wear out my cam, and should i just buy the electric pump?

I had a problem with my carb pouring gas into the intake after the car was shut off. I have an electric fuel pump, but here is what was happening to my engine. When I swapped the engine, I pulled out the charcoal canister. There is a vent hose that runs from the charcoal canister to the fuel tank. There is a valve on that line that needs vac pressure to keep the line open and venting. Since I had disconnected all of that it was causing vacuum to build up in the fuel tank and causing fuel to flow through the lines, into the carb and through the venturis. The easiest way to recognize was after driving the car I could unscrew the gas cap and get a huge rush of air into the fuel tank. This would last for hours after I had ran the car. Now I don't know if a mechanical fuel pump would do the same, but its something to ponder.

do you mean that canister that sat on the passenger side under the hood?that

do you mean that canister that sat on the passenger side under the hood?and does it look similar to a big coffee can? or do you mean the round one that goes under neath the fender?

they are both disconnected because i painted my engine bay and i thought that thing controlled the cruise control.

Thank you. It's always nice to have accurate information to work from.
That's good to hear (and would have been nice to hear earlier).
As already stated, cylinder compression has absolutely no effect on the fuel pump. They never "talk" to each other.
I wouldn't worry about it wearing out the cam. If it was a problem, you would probably have issues even mounting the pump (beyond the "normal" hassles of the job). Small and big block Chevys use the same rod.

Yeah looks like a coffee can. On mine there was a hose that connected to the cannister and ran to a metal line that went back to the fuel tank. On that line there is a round flat looking valve that has a vac port on the top of it. I just removed that and all was well. The easiest way to see if thats your problem is to looking down into the carb after you run the engine for 15-20 minutes and see if you can see fuel flowing out of the venturis after the engine has been shut off. Also you can unscrew the gas cap after you've driven the car and listen for a big rush of air into the fuel tank. Its something you would noticed when you unscrew the gas cap.

thanks for all of the input guys, i really appreciate it. i'm going to work on the car this weekend. i have school after work so the only time i have is the weekend. with all of the info you have given me, i should be able to fix this problem soon.
wrsjr you said that you removed the round flat looking valve?

same problem here i disassembled my engine and found a blown head gasket and a detonated piston all the way trough. also a second piston was all full of little holes like erosion (don't know the word in English for it picado) its a 350 with carb quadra jet one thing i notice was the idle control makes a lot of rattling but only when the computer its hooked up obviously cuz it controls it although i don't think it should rattle like that. Also i found fuel on the line going to the canister from the carb but no fuel in the canister at all.

i reinstalled my canister and connected my vacum lines. i went a few miles up the street and everything seemed to be good. not sure yet though, i havent had a chance to change my plugs or install a fuel pressure gauge. i will do more work this weekend once i get home from the car show at lowes motor speedway. now i have to buy a starter because it started hanging up on me.once i replace the starter and plugs i'll be able to push it a little harder and that will tell me if i'm getting gas in my oil. i pray the canister was my problem!

what sup guys,

whats up guys,
i changed my oil, installed plugs for a 1967 327 vette, connected the canister. my problem is solved!
i had major starter problems, the housing kept breaking off the starter,after breaking the housing off of 7 starters, i had to get a metal housing starter from 1967.
i cruised the car around yesterday for about 80 miles. i havent seen any gas in my oil and my starter is working like a charm. thanks for all of your help!!

so is it fixed?

yes sir, it is fixed.

was it the charcol can? cuz i have a HSR and i wanna clean up my engine bay, but not if it causes problems like that

wsrjr swapped out his 305 for a 350 and he was having a similar problem. so if i were you, i would clean it up and put it back. i'm not sure if the plugs were my problem or if it was the canister. either way, i would leave that thing alone.