Plumbing oil filler neck to exhaust

[John Larkin]

I'm getting tired of finding oil blown onto the valve cover from the oil filler neck after running the car hard. A racer friend suggested plumbing the valve cover to the exhaust to use the scavenging vacuum effect of the exhaust flow (sorta like the stock setup to the turbo inlet only downstream). Since alot of pro-stockers and rails use this type plumbing, would it be a bad thing for these cars?

 

[Tow Man]

Well..... It may work if you constantly run an open down pipe. The exhaust would have to flow freely across the check valve to create a vacuum! Any type of exhaust system will give you some back pressure rendering the check valve useless!

This set up is only used in open header applications!

If your that concerned about oil blowing out of the breather cap, maybe rig up an old road draft tube setup. This will be just as effective as an open element breather and still provide some scavenging at higher vehicle speeds. Any oil that blows out will just drip out of the tube under the car.

This is very old technology but worked for decades before PCV valves.

 

[Lee Thompson]

oil

John, IF you don/t have an after market check valve in your PCV line, you are probably pressureizing the crankcase under boost and it is coming out the breather. Quit possibly a new PVC valve might cure this problem as they are some what of a check valve.

 

[John Larkin]

Thanks Lee and T-Man. I think I have an extra brake booster check valve in stock from days gone by. I wonder if that would work.....I'm using a real ACDelco PCV.

 

[TurboDave]

Originally posted by John Larkin
I'm getting tired of finding oil blown onto the valve cover from the oil filler neck after running the car hard. A racer friend suggested plumbing the valve cover to the exhaust to use the scavenging vacuum effect of the exhaust flow (sorta like the stock setup to the turbo inlet only downstream). Since alot of pro-stockers and rails use this type plumbing, would it be a bad thing for these cars?

I seriously doubt you'd gain that scavenging affect unless you plumbed into the down pipe.

Remind your racer friend that these are turbo charged cars, and as such there's a significant amount of backpressure in the exhaust manifolds, created by the turbo. The backpressure is always there, but gets even worse as boost builds.

 

[John Larkin]

Yes Dave, precisely. The downpipe would be where I think it should be tapped. In that case, the oil filler neck wouldn't be the best choice since it's on the wrong side of the engine. But the PS valve cover is ready to go if I used the old stock breather where the K&N is now and plumbed off it. Now I just have to decide if I want to drill a hole. I think the highest vacuum signal you could possibly achieve would be just south of the elbow, plus it would be the hottest exhaust temp post-turbine to "burn up" the oil that made it in there.

 

[re-evaluating]

How much oil does your motor leak now?

First off are you running full exhaust? I think I know the answer to that but if you are it will not work well to say the least. We saw a real difference on a normally aspirated motors with open headers so back around 95 or so we tried installing a evac in the downpipe. (running THDP with dump open) In short it pressurized the crankcase to the point it pushed out all the seals that weren't leaking before. The best solution in my opinion is to use a electric vacuum pump off a Roadmaster. Just my opinion Dave

 

[John Larkin]

Yeah, full exhaust. So if I read what you are saying, the benefit of exhaust scavenging for a vacuum effect is only applicable when the tap point is at the end of the "collector" or exhaust. If it is upstream of that location, then the tap point becomes just part of the exhaust and it is pumped into the engine instead of creating the intended vacuum effect. I guess Lee has the best solution or like you say, the pump; I'm not hardcore enough for the pump, yet anyhow. Odell runs one though.

 

[The Radius Kid]

Originally posted by John Larkin
Thanks Lee and T-Man. I think I have an extra brake booster check valve in stock from days gone by. I wonder if that would work.....I'm using a real ACDelco PCV.

Interesting idea,that one.FUBAR and I have been tossing around the idea of using a check valve from something like a Honda Prelude or Accord[4 cylinder job?].Should be about the right size and have the right vacuum characteristics,if my guess is correct.