PCV valve...?

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Nate Nagel - 12 Apr 2006 01:49 GMT

OK, as some of you probably are aware I have a '55 Studebaker with a '63
Studebaker engine in it. The PCV valve attached to this engine has
ceased to perform as a valve, it's more of a metered orifice at this
point. After several dousings with carb cleaner it still won't "check"
when I blow through it "backwards." There apparently is no modern
replacement for it; or at least none that any manufacturer of auto parts
will admit to. It's an inline valve, using 5/16" hose. (or is it 3/8"?
I forget.)

which is better, just running my "busted" valve, or finding one that
will fit (but may not be calibrated to exactly the same flow rate as the
original?)

...or does anyone have a magic interchange book and can tell me what I
need to buy? This is a 289 4-bbl.

I'd rather not have to swap in a road draft tube; my goal here is to
have an old car that doesn't smell like one when I drive it.

thanks,

nate

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Steve W. - 12 Apr 2006 02:37 GMT

Should be fine if you can find one that is off a vehicle with a similar
sized engine. Seems like the one from a few small blocks have tube
fittings on each end even when they go into the VC on the engines.

http://www.mystudebaker.com/cats/studebaker_carb_fuel/pcv_rel.htm
Has the correct valve if you need it.

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Steve Williams

> OK, as some of you probably are aware I have a '55 Studebaker with a '63
> Studebaker engine in it. The PCV valve attached to this engine has
[quoted text clipped - 18 lines]
>
> nate

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N8N - 12 Apr 2006 15:02 GMT

Thanks, I forgot about Stephen Allen's - I tried SASCO and Chuck
Collins and they were out.

nate

> Should be fine if you can find one that is off a vehicle with a similar
> sized engine. Seems like the one from a few small blocks have tube
[quoted text clipped - 40 lines]
> http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
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* - 12 Apr 2006 16:29 GMT

Steve W. <Dugdug56@what.com> wrote in article
<1144805631_21409@sp6iad.superfeed.net>...

> Should be fine if you can find one that is off a vehicle with a similar
> sized engine.

Actually, it has more to do with the amount of vacuum an engine produces.

Different camshafts in the exact same engine will affect the vacuum signal.
This doesn't even take into account same cubic inch, different intake
system, different engine designs from different manufacturers.

The compression rating of the spring inside the PCV valve is based on the
strength of the vacuum signal.

The spring allows the poppet valve to seat against the intake side of the
PCV at idle, then float off the seat to allow crankcase vapor flow when the
engine goes off-idle.

When the engine is shut off, the spring closes the poppet valve against the
crankcase side of the PCV to keep vapors from escaping into the atmosphere.

I've seen look-alike PCV valves that stayed seated against the open side
and never "floated" due to a spring not being calculated to overcome the
vacuum that the engine produced off-idle.

Best way to "match" PCV valves is with a vacuum pump and guage.

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N8N - 12 Apr 2006 16:33 GMT

> Steve W. <Dugdug56@what.com> wrote in article
> <1144805631_21409@sp6iad.superfeed.net>...
[quoted text clipped - 23 lines]
>
> Best way to "match" PCV valves is with a vacuum pump and guage.

So what you are saying is that the PCV valve actually relies on
crankcase pressure to open rather than engine vacuum? FWIW this engine
pulls about 18" of vacuum at idle but I will be installing an Avanti
cam in the next few weeks (because more power is always better) so I
don't know that that will remain the same, although the Avanti grind is
still pretty mild

nate

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Hugo Schmeisser - 13 Apr 2006 02:55 GMT

> So what you are saying is that the PCV valve actually relies on
> crankcase pressure to open rather than engine vacuum?

Nothing "sucks", Nate. Everything "blows".

Vacuum has no power. Pressurised air does.

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* - 13 Apr 2006 16:07 GMT

N8N <njnagel@hotmail.com> wrote in article
<1144856001.595872.55690@j33g2000cwa.googlegroups.com>...

> > Steve W. <Dugdug56@what.com> wrote in article
> > <1144805631_21409@sp6iad.superfeed.net>...
[quoted text clipped - 23 lines]
> >
> > Best way to "match" PCV valves is with a vacuum pump and guage.

> So what you are saying is that the PCV valve actually relies on
> crankcase pressure to open rather than engine vacuum?

I never said or implied anything like that. Don't go putting words in my
mouth.

As engine vacuum decreases from idle to WOT, the spring will overcome the
decreasing vacuum, and move the poppet valve towards the center of the
housing, allowing crankcase vapors to pass into the intake manifold.

As the engine returns to idle, the increasing vacuum overcomes the spring
pressure and seats the poppet against the intake - or vacuum- side of the
housing.

> FWIW this engine
> pulls about 18" of vacuum at idle but I will be installing an Avanti
[quoted text clipped - 3 lines]
>
> nate

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N8N - 14 Apr 2006 15:12 GMT

> N8N <njnagel@hotmail.com> wrote in article
> <1144856001.595872.55690@j33g2000cwa.googlegroups.com>...
[quoted text clipped - 50 lines]
> pressure and seats the poppet against the intake - or vacuum- side of the
> housing.

I'm just trying to understand how this all works, as I have to admit
that I've never given much thought to them before, and have just
installed the factory recommended replacement parts whenever the old
ones seemed "sticky" or otherwise nonfunctional. So the check valve
should actually be installed backwards from how I was originally
envisioning it it sounds like? IOW the passage is only open when
vacuum is *low* not *high*...

nate

> > FWIW this engine
> > pulls about 18" of vacuum at idle but I will be installing an Avanti
[quoted text clipped - 3 lines]
> >
> > nate

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fiveiron@webtv.net - 14 Apr 2006 23:40 GMT

what do you have to loose if you replace the flexible hoses / fittings /
pcv valve with new parts that will "fit" -

using something that would be comparable / compatible to / with the
size engine you have?

when you replace the flexible hoses - the old valve might kick-in.

nothing ventured, nothing gained - get with it.:--)

mho

vfe

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