Hello Everyone,

Just rebuild a 455 olds to put in my 79 t/a. the engine has

shallow dish pistons
stock c heads
valve job
290/300 voodoo cam
edelbrock 2516 intake
750 quick fuel dp

the problem im having is my oil keeps getting thinned out by gas? i have no idea where it could be coming from. but the engine runs for about 10 mins before the oil gets to thin and my pressure drops. any ideas?

thanks for the help!

 

Welcome. It's not in your best interest to resurrect a five year old thread, as people can get confused by the prior posts. I moved your post to it's own thread.

There are two possibilities for the source of the gas in the oil, either a leaking carb or a bad fuel pump diaphragm (assuming you have a mechanical pump). If the carb were flooding, the engine would run very rich and you'd know this before the oil thinned out, so my money is on the fuel pump.

 

Thank you for moving my post to its own thread. My fuel pump is a electric holly and its set at 6psi roughly. i do not have a regulator for it tho. but it is running rich because i haven't tuned it yet. but the oil is getting so thin so fast.

 

So when you pull your dipstick and put the the oil off it up to your nose you smell gas?? And what are you calling fast and thinning??

 

yes, and its so thin. it takes the car 5-10 mins to thin 15w40 to like water. my oil pressure drops for the oil being so thin that i have to turn the car off. also the lifters and rockers start screaming at that point

 

What do the spark plugs look like and have you driven it like this, and if yes how did it drive.

 

Well, if you don't have a mechanical pump, then obviously the only place you can get fuel is from the carb. I can't believe the carb can pump that much fuel into the engine and still have it running. Are you SURE it's fuel? Keep in mind that for that much fuel to thin the oil, the oil level would go up at least a quart. Is this happening and do you drain the oil out every time? If not, then your problem can't be fuel in the oil. More likely you have either loose bearings or a worn oil pump that causes the low oil pressure once the oil heats up and thins out.

 

they are fouled and i have not driven it. its only ran about 20 mins since ive built the motor

 

there is extra oil in the pan each time. yes i have to the motor starts screaming because its like water. the oil pump is new so i hope its not that. the bearings are also new

 

Ouch, so this basically happened at breakin.

 

yes, my break in was cut short:/ by afew mins

 

You don't have another carb you know is good do you??

 

Then figure out why the carb is dumping fuel in the engine. Could be a stuck float or some other problem.

 

Like crud coming out of the fuel tank hanging the needle and seat open. Check both front and back needles.

 

Okay! I will check the carb, I'm no wizard with carbs so I will have to look up how to do that

 

Okay! I will tear the carb apart once I look up how to do that haha

 

None are a wizard with carbs, just some are better than others. Also we started out thinking we knew it all, but knew little, and had a lot of learning to do and still learning. The reason I suggested to look at the needles for crud/grime on them is I saw this on a 72 Plymouth 2 barrel where I tore it down and put a new needle and seat in and it did it again in minutes of starting. The gas tank was full of mainly rust, and when it got to the needle and seat flood city, since it couldn't close. Cleaning the needle and seat only worked for a few minutes before more rust came from the tank and screwed it up again once started.

Lets us know what ya find.

 

Carb should have sight glasses on each side so it's real easy to check float levels. They should be in the middle.

 

I'm still trying to imagine how this problem can be occurring.

We're talking about passing enough fuel past the rings to visibly dilute the oil and raise the oil level, over only a few minutes, and still have the engine able to run.

How does the engine sound when it's running?

Do all of the plugs look the same, or are they different?

Maybe if one needle and seat were stuck open, and the other was correct, half of the cylinders could be running and half could be pushing liquid fuel past the rings, but you'd barely call that "running," and I'd expect clouds of black smoke.

- Eric

 

Yeah, this is what I'm struggling with also. I don't understand how this is even possible.

 

Oh I bet there is a long story behind it. Remember he knows little about this and he is only 25. May have had less than experienced friends over observing or helping. He or they think its this or that....20 minutes later, with engine rattling, and fouled plugs and diluted oil that he finds even later.

 

I'm really not trying to criticize here. but as you know, long distance diagnosis with potentially incomplete information is difficult at best. As I pointed out above, unless there's sabotage, there are only two places where fuel can enter the oil, either through the fuel pump diaphragm or down the carb and past the rings. If there is no mechanical fuel pump, that path obviously goes away, leaving the carb as the sole source. Many here have pointed out that for that much fuel to leak out the carb and into the crankcase required a very high flow rate. If that much excess fuel is leaking while the engine is running, it's likely the engine would stall and you'd see billowing clouds of black smoke. If, however, the float is stuck or the fuel pressure is too high and the electric fuel pump is left on when the engine is NOT running, well, that's one possible scenario.

 

Well he did say it ran for 20 minutes, and may have had the throttle open wide, to get it to do so with it that rich. The electric fuel pump may be the biggest problem, but who knows, but he has to do the work to find out and report back. Sabotage possible, but a pretty remote possibility imv.

 

im going to check the needle seats in the carb as well as the floats. i also will get a regulator and set it to 5psi. im going to check compression and all the plugs. i will report back with what i find! thank you for all the info and help everyone!

 

We will be interested in hearing what did happen.

 

hello everyone,

just finally getting back into working on the car. sorry for the delay! but i did a compression test and every cylinder is 150 psi. also took apart the carb and checked the power valve which was good. i cleaned the jets but im not expert with carbs. added a fuel regulator and i am running 6psi right now. car ran again for 15-20 mins idle to 2500 rpm and the gas just started to thin again... im thinking this carb is shot. what does everyone else think?

 

Did you clean the emulsion tubes and check the float level and needle and seat???

 

problem solved! everything in the carb is fine. i did find afew loose intake manifold bolts but the gas in the oil issue is from cylinder 8. for some reason the piston hit that plug and closed it. so that cylinder has not been firing.. the weird part is i didnt hear a miss at all but my cam is pretty choppy. im still stumped on why it hit tho but i just shimmed it out a 1/16 and its not hitting any more. none of the other cylinders hit so that really has me stumped.

 

Either that's the wrong plug or someone dropped it before installation without checking it first.

 

just 1 plug not firing caused that much fuel to get into the oil?????

 

I've had cars run for miles with a dead cylinder and not effect the oil, something doesn't seem correct here. Are you changing oil every time you see that it is thin? Could it be that you are looking at hot thin oil and comparing it to the thicker cold oil you just put in.? Does the oil smell of gas, will the dipstick light up if touched with a match? Something is a miss here.... Tedd

 

thats all i can tell at this point. i need to change the oil again and run it and see if it stops. but yes the oil has gas in it and its not just thin. you can smell it and also see it in the oil. but that dead cylinder had aton of gas in it. plus the engine is still running rich up to when i got the car idling.

 

I have to agree.

Years ago a buddy of mine towed a trailer cross country with a '67 Newport, and found a spark plug wire off when he got to California.

Never noticed any performance problems, and had no changes to his oil.

- Eric

 

okay so do you guys possibly think i just have a bad oil pump? this one runs fine for about 2 mins and then loses pressure. this is going to sound dumb but i had this pump in my 403 for about a year and it had less then 1000 miles. but that motor spun a rod bearing in the driveway. i get about 30-40psi at idle for a min and then drops to 10-20psi. so then i added a quart of oil because it sounded like it was starving and it jumped to 60-80 for a spilt second. then back to 20psi. so im guessing that pump is shot.

 

Does anyone think the grade of oil could be an issue. Do you guys run 15w40 in your older engines? Back in the 70s and 80s we ran straight weight oil. That was in So. Cal. Though.

 

im running 15w40 right now and after my 10-15min run today again my oil stinks of gas and is like water. so that may also be my pressure issue. im completely out of ideas at this point

 

Perhaps it is the Olds/Pontiac curse!

 

 

Could it be that the engine was bored but had standard size pistons installed? Strange that you had any compression at all. Could the engine builder have put the wrong wrist pins in? Definitely sounds like you have a mystery to solve.