Well not quite either. The block draws in nothing from the
outside, except when shut off and cooling down. The PCV (or Positive
Crankcase Ventilation), valve actually keeps the engine from drawing any
fresh air into the block while running. Fresh Oxygen mixed with
unburned residue from the piston ring blow by, and a Blast of flaming
blow by can cause an explosion in side the block, blowing the pan, oil
filter, valve cover or any other easily removed piece right off of the
engine. My grand father used to tell me about case tractors doing that
all of the time back in the teens and twenties.
The reason the tube from the filler neck is connected to the
inside of the air filter is so that there is a little extra vacuum to
draw out the vapors of the blow by and heated fumes, and then in turn
burn those again.....in a safe manner. The later Alpines at least had
the addition of the little round canister with the tube on opposite ends
and opposite sides. This typically fills with oil mist residue and
needs to be drained and blown clean once in a while...at least mine did.
It seemed to act as both a flame suppresser, (you don't want open flame
going back in to the block...see above), and as a filter trap for oil
mist. Mine also use to plug up with white mush, when my head gasket was
leaking a bit of water in to the oil. A tell tale sign of a bad head
gasket and/or a warped head. Mine had both.
Rich.
> ----------
> From: w1gsl(at)MIT.EDU[SMTP:w1gsl(at)MIT.EDU]
> Sent: Monday, March 10, 1997 9:40 AM
> To: edalsj(at)igs.net
> Cc: CMottram(at)aol.com; alpines(at)autox.team.net
> Subject: Re: I can't breathe (fwd)
>
>
> To: CMottram(at)aol.com
> Subject: Re: I can't breathe (fwd)
> Cc: alpines(at)autox.team.net
>
> >My S III had individual air filters for each carb. The rear air
> filter had
> >the tube fitting out the back, which was connected to the similar
> fitting
> >on the oil filler neck with an appropriately sized hose. This in fact
> >provides some of the crankcase ventilation. The front air filter had
> a plug
> >in place of the fitting, presumably so that it could be interchanged
> with
> >the rear one if necessary.
>
> >John S.
>
> Close but not quite..
>
> Both fittings on the air cleaners are connected together through a
> special
> molded hose which connects to a flame arrestor connected to the oil
> fill neck. The crank case vent system breaths "clean" air in through
> the air cleaners.. into the valve cover, on through the sump where
> vacuume
> from the manifold sucks the blowby through the PVC valve...
>
> Steve F
>
>
> **********************************************************************
> *********
> Steve Finberg W1GSL
> w1gsl(at)mit.edu
> PO Box 397082 MIT Br Cambridge MA 02139-7082 617
> 258 3754
> **********************************************************************
> *********
>
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