Oil choking my carb

[Mike Bradbury]

Since the recent rebuild of my 350, I have noticed that my carb has been coughing but only when it is cold. I thought it was just an issue with cold weather and it needed to warm up, but then when it was warm and it was still doing it I thought it might be something else.
This is only a weekend truck so after a year I only have 2500 miles on the rebuild.

One day I noticed that there was oil in my air cleaner! weird since my PCV sucks in the bottom of the carb any oil should be burned off or sucked into the combustion chamber.

I believe that the baffle plates that were welded onto the after market valve covers are too small to let only crank case gases by and it is actually letting oil by too. So I made a little device that will effectively separate the oil from the gasses. To test this theory I pulled the line into the carb, so now it was a passive system rather than an active system being drawn through by the carb. sure enough there was oil being sprayed on my valve covers through my after market vents.

Here is the device I made. It made it's first appearance at the Brother's Truck show this weekend, and I got many questions like; "what is that thing?"
In 250 miles of driving I got about a teaspoon of oily gas blow by residue. I have some questions for the guys at Crower and my engine builder as to why there is so much but here is some pics I snapped of it.





This is what is inside the can






There is a drain on the bottom



A screen filter on top



The top clamp





The carb plate



Here is what I caught after 250 miles

[ole dollor]

first question i have is your motor using any oil ? and are you sure your pcv system is working prop.

[Rufton]

PCV valve cover baffles must not be working very well; I've had similar issue.
Twould be nice if oil separator drained oil back into valve cover; maybe version 2.0
Well, it works and looks kinda cool

[Mike Bradbury]

On the original stock valve covers, the plate has a whole baffling system before it even gets to the PCV. These aftermarket V.C.s only have a small plate of aluminum welded under the breather hole. It is a newer Eldelbrock carb with plenty of suction, and I installed a brand new PCV at the time of the rebuild. I do have some questions for the builder and Crower because I think something might be shredding inside the engine. If you look at the pic of the oil in the bottom of the container you can see little bits of shiny pieces. they are not magnetic so I think it is just in the beginning stages of wear but still way too premature.

[Rufton]

I like to cut every filter and inspect element.
Good way to see if glitter getting progressively better or worse.

[Lee H]

High mike, I saw the separator at brothers and suspected you were having a blow by issue but did not get a chance to talk to you. I also did not know you had a fresh rebuild, given that its time to have a sample of your oil analyzed to find out what is breaking down. Lee
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[Mike Bradbury]

Yeah that is why I saved it in the container. When I first opened the separator it smelled much more like crank case gases but after a couple of days it smells more like oil. It always looked like oil but the gases have evaporated and left just the oil.

[Lee H]

You, Crower, and your engine builder will want to know what's in the oil and will provide relevant data. I would get two samples analyzed, one with the oil in the separator you have now and one with a fresh oil change and 500-1000 miles.
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[Mike Bradbury]

Who analyzes oil?

[Lee H]

There's a bunch of them, just Goggle. Check out the process and a few sample reports to see if they will work for you. I used one about 10 years ago to prove to a builder that there was to much metallic floating in the oil after he looked at it and said that was normal for a fresh engine with only a few thousand miles. Turned out he did not machine the front of the block enough so the double roller chain finished the job. Good cleaning, new bearings, rings, and I was good to go. Engine now has 70K and no issues, does not burn any oil and gets used hard.

[Jack_71C10]

I'm not a mechanic so I may be wrong, but I've never owned a car where the pcv line went to the vacuum on a carb. They have always went to the air cleaner, I don't think they need that much flow. I also think it would kill your vacuum. All my vacuum lines are closed, meaning there is no lose of vacuum.

[ole dollor]

Originally Posted by Jack_71C10

I'm not a mechanic so I may be wrong, but I've never owned a car where the pcv line went to the vacuum on a carb. They have always went to the air cleaner, I don't think they need that much flow. I also think it would kill your vacuum. All my vacuum lines are closed, meaning there is no lose of vacuum.

it should go to vacuum , thats how it works. double check yours ..breather tube hose goes to air cleaner...

[Don Quixote]

I am wondering if I am not having a similar problem. My valve covers are flipped I guess to make adding oil a little easier but the idea may be backfired by the fact that there is where all the oil pressure is.

A theory unto this, could I add an inline fuel filter to absorb the oil before going to the carb? I have an open element ait cleaner and my carb has the PCV port on the bottom?

As it is, I am puffing a little smoke at high vacuum and I had thought it might be a ring or a valve seat but this thread got me thinking...

[Lee H]

If you getting oil going through the PCV system to the carb you either don't have good, or any baffles in the valve covers or your engine is producing way to much blow by, indicating an over haul is needed. After market valve covers are notorious for allowing oil to be sucked into the PCV hose.