I got the part about the hose being connected upstream of the carb, but
what threw me for a loop was the original text. It thought the original
problem he had was oil leaking from the engine due to positive pressure
in the sump. It also sounded like he already had the appropriate
breathers on his valve covers, yet his engine was still leaking. I
interpreted that his problem was fixed after he implemented your
solution, but it looked to me like the only difference between his
original configuration and your configuration was the intake hose from
the air-filter to the valve cover. If his problem was over-pressure in
the sump, adding another hose to the valve cover would vent the sump
gasses into the filter, not the other way around since gasses go from
high to low pressure areas. Thats why I asked if his problem was solved
by an extra outgassing path from the sump, rather than sucking fresh air
into the sump which is above ambient pressure when the engine is
running. However, I get the feeling that I missd some of the
conversation, and probably some of the relevant details. Sorry if I'm
confusing things.
James J.
Jim Stuart wrote:
> Inlet air, if required, is from the AIR CLEANER, not the carb. This
> provides clean air without road dirt. Excess pressure from the crank
> case is bled off through the valve cover, through the pcv valve - a
> one way valve- & into the erg fitting- the large center tube- at the
> carb base. In the old days, & in many of our 4 cyl MG's, the vent was
> from the engine side cover directly into the atmosphere. The clean air
> rules demanded that the dirty air be recycled, so the pcv valve-
> "positive crankcase vent" was developed to send the nasty air back
> through the carb where it becomes part of the next combustion cycle.
>
> If blow-by is minimal, you would not necessarily have positive
> crankcase pressure, especially at low rpm's. In extreme cases, the
> intake air may become another outlet, since it is not protected by a
> one way valve.
>
> I don't design or necessarily understand all the automotive systems,
> I tend to copy the ones that work.
>
> Jim Stuart
>
> -----Original Message-----
> From: JJJ [mailto:m1garand@speakeasy.net]
> Sent: Tuesday, May 20, 2003 10:49 AM
> To: mgb-v8@autox.team.net; jimbb88@usa.com
> Subject: RE: Rover 3.9 Engine Breathing?
>
> I'm a little confused, though I don't doubt that it works. Since
> the pressure in the crank case is caused by piston ring blow-by,
> the sump should always see a positive pressure (which causes the
> oil leaks). I can't envision a time when the sump would see a
> vacuum and suck in air from the filter base. Are you sure that
> this fix isn't just giving the engine another path to vent pressure?
> Just Thinkin' out loud. Maybe I'm not picturing it right.
> Cheers,
> James J.
>
>
> --- Jim Stuart <vze3swyy@verizon.net
> <mailto:vze3swyy@verizon.net>> wrote:
> > I removed the small "mushroom" fitting & tapped the
> > hole for 1/4" pipe,
> > added a 90` fitting & an in line pvc fitting to the
> > center large pipe on the
> > front of the Edelbrock. One flame trap was cleaned
> > out & a rubber line run
> > to the base of the air cleaner. This provides clean
> > air intake to the sump,
> > the pvc is the outlet vent. All nice & clean, &
> > politically correct.
> >
> > Jim
> >
>
>
>
> .
>
>
>
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