[Fot] Crank case evacuator question

[Chuck Arnold and/or Kathleen Kelley]

I could easily do that setup as I have a catch tank in place now.
BUT... How would negative pressure work in such a case as I would be sucking
on the tank with an opening to the atmosphere and I do not understand how
any negative pressure would get applied to the crankcase.

If Iran the evacuator line to a non-vented tank then to the rocker cover
[with a cover over the vent hole like Christian showed to stop directly
sucking into the hose] then I think it would work.  The evacuator uses 5/8
inch line -- which I believe is AN10.

Thoughts everyone?



On Fri, Aug 26, 2011 at 10:56 AM, Robert M. Lang <lang at isis.mit.edu> wrote:

> Hi,
>
> With a crankcase evac, you'll have negative pressure present, so if you tap
> into the valve cover, you'll pull oil mist out. Another way to do this
> without sucking all the oil from the engine is to set up a system where the
> valve cover vent line goes to a tank of some sort that has the evacuator on
> one tap and there is also a vent to atmospere. That way, if the engine
> starts blowing oil, it goes to the tank but not necessarily all out the
> tailpipe.
>
> The goodparts oil seperator is a good way of doing this, but you may find
> the capacity to be on the small side. So another way of doing it would be to
> use the goodparts setup with a larger tank...
>
> I run a PCV setup on my car. I have the neg. pressure source as the INTAKE
> (there's a tap on the Cannon Weber manifold). This gives me negative
> pressure on the overrun only. If the crankcase pressurizes, it vents to the
> catch tank (which is vented to atmosphere). The key here is that when
> there's lots of oil present in the valve cover - it "blows" into the catch
> tank, but when I lift, the oil vapor can get sucked back through the into
> the intake (and burned off). With this setup, I get a small amount of oil in
> the catch tank when I run the motor to stupid revs (like 7000+), but no
> excessive leaks anywhere.
>
> To your question on the breather - I wouldn't use the oil filler cap as the
> breather (along with the fitment issuse you mentioned (like fouling on the
> bonnet)). Use the catch tank as the breather. That way you don't have to
> worry about saturating the breather filter and the potential fire hazard
> that presents. The key here is that on a long hi-RPM run, you get a LOT of
> oil in the valve cover and there's a good chance that that oil will find its
> way out. I don't like valve cover breather filters cuz they seem to fill
> with oil and then drip (or worse) and you get oil everywhere.
>
> On the size of the hose(s) from the valve cover - go with TWO AN8 or AN10
> lines if you can.
>
> regards,
> rml
> ------------------------------**------------------------------**
> ---------------
> Bob Lang              Triumph TR6!!            |  This space for rent
> Former NER Solo Chair                          |
> Voice:617-253-7438                             |  Cell: 339-927-4489
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-- 
Chuck Arnold and Kathleen Kelley