The Stovebolt Site Forums The Shop Area Engine Shop Road Draft Tube - Deve's PVC

My Road Draft Tube always has oil coming out!. Is this normal?

If oil is not coming out anywhere else, consider yourself lucky. It is "normal" on an engine with lots of miles, blow-by, etc.

Thinking about the changing over to something like the Deve's PVC kit.

Anyone done that?

It looks intriguing but I think the pcv valve might be too low on the engine. Will the intake manifold start sucking oil out of the crankcase? I'm sure someone here might have experience with it to share.

With the road draft tube, the air has to travel up about a foot or so through a filtering mesh to keep the oil inside the engine.

If it works, it's an elegant solution without the need to hack up the valve cover.

Better buy some stock in an oil company if you use that Rube Goldberg setup. The PVC needs to be up around valve cover height on a baffled standpipe like the factory system to prevent liquid oil from getting drawn into the intake.
Jerry

Are you missing the baffle in the crankcase that shields the opening from oil splash?

Don't know, if I pull the tube will I see the baffle?

Is there any type of maintenance that is required?

Do you have a breather cap on the oil fill? Every vent. system needs 2 in & out openings for circulation.

George

I soaked my draft tube in kerosene and let it dry. Worked well.
Good luck

Not saying this is what you SHOULD do…

But I placed a breather with PCV in the valve cover (from there connected to manifold vaccuum), and modified the road draft tube to be the source of clean filtered makeup air. Seems to work fine. But I haven’t done any really scientific testing.

I will say that it’s a big improvement over the blow-by just venting out of the draft tube and valve cover.

Kilroy55 Other bolters mention a filtering mesh in theolden days we called that "hog hair"coarse fiber like in an oil bath original air cleaner. Might go thru your oil fill cap (that has modern "hog hair" with a PCV hook up. So true though that if that is your only oil leak your very lucky !! My side of our garage apron has some territory marks from my 51 !! It gets worse when I work on it too LOL.

I used the factory PCV setup on my 261, which uses the stand-pipe Jerry mentioned. I did not tap into the air cleaner for make-up air but rather used a filler cap with oil-soaked metal gauze for a filter. I figured that's what the factory put on for the road-draft setup so it was probably good enough for the PCV. Wrong. This works but only up to a point, that being if you run zero vacuum for more than a few seconds you can start to smell blow-by. As soon as the vacuum comes up to say 2"Hg the odor goes away. If there's no vacuum in the manifold the blow by will come out the breather; whereas with the road-draft system even at zero vacuum there is enough draft from the air moving by to create a draft so the blow by goes out the road-draft tube.

This is probably not an issue on a truck driven around town or on local farm roads etc. where zero vacuum rarely occurs but on a highway rig where you're pulling long grades at full throttle it's a problem. I will fix it when I get home from the long road trip I'm on.

Yes, it makes much more sense, than the PCV conversion I see a lot, where they just pull out the draft tube completely, stick a PCV valve in that hole and call it a day (and than wondering why the valve is full of oil).

The gases evaporating from your oil tend to go upwards - so sucking it out at the highest point ( i.e. valve cover) seems to be a good idea in my book.
I mean - did you ever see a V8 with the PCV that goes down in the crank case?
They are all at the valve cover - I guess the GM engineers knew what they where doing.

I left the oil filler tube portion of my downdraft tube in place (just cutting the actual downdraft part and welding it shut - so it's just a oil filler tube now), also I put a filtered breather cap on it.
So I got circulation from the crankcase to the valve cover, and not vice versa - like a lot of folks do for some reason.

Frank

Yep, I have a vent cap on the valve cover.